How important is low W & F performance anyway?

@OP. There are two factors at issue here. The first, if I understand you correctly, is that you claim that your measurements differ from the manufacturer's published specifications - please correct me if I am wrong in that.

But it would be helpful if you could go into more detail about your measurement protocol. I presume you have an NDA with the company you were working for but it would also be helpful if you could provide details of the other two turntables - their manufacturer specification and your measurements.

The second thing is that like everything in audio, singling out specific performance measurements can be misleading because system performance  (i.e. the total performance of the device) is what really matters.

@yoyoyaya :  All of the tables in question have encoders attached to the platter, used for feedback to the motor controller.  This gives a very accurate picture of the actual platter movement and does not suffer from eccentricity or other defects of an LP test record.  I used proprietary polar plot software to measure and plot the frequency stability of the signal from the encoder which uses the 2 sigma method for computing W&F.  I also used Multi-Instrument software which has both RMS and 2 sigma which produced similar results to my software.  I have a piece of shareware W&F meter, a Leader LFM 39 W&F meter and an Agilent 35655A dynamic signal analyzer for spectral analysis.  All of them produced similar results.

The one I worked on used an optical encoder with 360K PPR;  the raw signal produced 50kHz at 33 1/3 RPM so I ran it through a divide by 16 circuit to produce 3125Hz which could then be analyzed by conventional means.

The first of the other DD tables used a magnetic encoder with 2560 PPR;  the raw signal produced 355.555 Hz at 33 1/3 RPM.  As I noted above, their published spec was 0.008% (no method given), but it measured ~0.8%.  It uses a coreless motor but I observed an 88.88 Hz lobing superimposed on the W&F signal which seems to correlate with the 160 magnetic poles on the encoder, in other words, it was cogging because of the magnetic encoder.  The motor controller used by this mfr has development software for programming and tuning the controller with the ability to monitor the motor performance and it showed the same cogging anomally.

The second DD used an optical encoder with 10K PPR; the raw signal produced 1388.88 Hz at 33 1/3 RPM.  Their published spec was 1 PPM (0.0001%) but it measured ~0.16%.  The motor was a NEMA17 BLDC motor with iron core stators which of course, will have cogging between the PM rotor and the pole pieces.  This was clearly visible on the plot.

Answer, if you cannot hear it, it does NOT matter, and published specs, ridiculously low, are a marketing game.

I've been given, inherited, and purchased a good bit of Vintage Equipment.

I think it is fair to say that old published specs compared to modern: Vintage Equipment has higher distortion, higher wow and flutter specs (real or marketing numbers).

And yet, when you listen, and end up preferring that Vintage equipment, you learn that the low decimal numbers do not translate to 'better'. 

My Fisher 80 az mono blocks, made in 1958, were rated at 30 watts per channel at 0.5% distortion, I have seen many Vintage manuals that showed power levels at 1.0% distortion as a threshold.

https://www.fisherconsoles.com/non%20console%20manuals/fisher%2080az%20sm%20om.pdf

When Steve Leung at VAS heard I was going to sell them, he made me sell them to him. I was just there to pick up a friend's cartridge he rebuilt, and Steve mentioned he had finally found time to listen to them, with a big smile.

My Thorens TD124 TT speed, you waited till it warmed up, refined the speed, and learned to check it once in a while, especially if a party and the room warmed up as more people arrived. Only very rarely could I hear the speed was off (young ears back then), most of the time I was surprised it had drifted and I couldn't hear it. No one at the gathering ever knew.

Technics TT's. I often recommend buying an SP-10, 15, 25, and I link this document to show that the specs of current models might meet, but do not exceed those vintage models shown on the bottom of the chart

https://vintagetechnics.audio/turntables.php

What is of concern is living without features, buying into 'straight wire with gain' that leads to no balance control, no stereo/mono mode switch, no rumble filter to help with slightly warped lps, no tape loop .....

Quickie AI:

"Wow and Flutter refers to speed variations in a turntable's rotation that cause audible pitch distortions in the music.  Wow is a slow fluctuation in speed, often once per revolution, typically caused by an imperfectly round platter, warped records, or off-center pressing.  Flutter is a faster variation, usually due to motor pulsing, bearing issues, or belt imperfections, and is perceived as a "warble" or "cracked" sound. 

• Audibility: Most listeners won’t notice wow and flutter below 0.25%, though sensitive ears may detect it at 0.10–0.20%.  Values above 0.25% are generally considered noticeable and problematic."

Audibility: Most listeners won’t notice wow and flutter below 0.25%, though sensitive ears may detect it at 0.10–0.20%.  Values above 0.25% are generally considered noticeable and problematic.

Therein lies my question:  How can a table such as DD1 have such lousy performance (0.8%) and still garner nothing but praise?

OP

"How can a table such as DD1 have such lousy performance (0.8%) and still garner nothing but praise?"

You had it, tested it, (lousy performance) but could you hear it?