LP grading:visual, play grade.. Goldmine standard?

I am wondering about LP grading.
To actually grade an LP. playing it would be needed.
But many sellers just visually grade it.
If an LP is graded 'visually', and the person grading it says "this is a Mint- Lp (according to Goldmine) is he/she saying thay stand behind it actually playing as a mint- LP?
Should they have to do so?
If not, in my mind, what good is visual grading at all. I mean you could grade them in a closet at midnight with the power off and then all your LPs would be mint!
I want to know what other think about this touchy issue of grading...
I look for two main things when evaluating: 1) Lack of major surface scratches and 2) I've learned to look for this over many years but you can get good at it too if you take the time to correlate dynamic range with appearance in your current sollection; the appearance of what seems to be good depth of the groove. By this I mean that the dark vs bright reflective subjective ratio of the playing surface is high; shiniest at the peak of the separating ridge from the darkness of the groove where the stylus will track. when "good" this subjective measurement has never failed in yielding pressings that are both quiet and that are high dynamic range. I wish I could provide side by side visual and audible comparisons to demonstrate this but it isn't hard to acquire the skill to do this. Happy hunting, feel free to get me to elaborate more on this topic if needed. Bottom line it works, requires a little skill development on the part of the reviewer (an art if you will) but yields much satisfaction. Obviously there were some mass market pressings for which this won't apply no matter how many pressings are evaluated. Cheers!
To quote the Goldmine standard for "Mint":

"Absolutley perfect in every way - CERTAINLY NEVER PLAYED, possibly even still sealed*. Should be used sparingly as a grade, IF AT ALL."

From the GM standard for "Near Mint":

"A nearly perfect record. Many dealers won't give a grade higher than this, implying (perhaps correctly) that NO RECORD IS EVER TRULY PERFECT...Basically, an LP in Near Mint condition looks as if you just got it home from a new record store and removed the shrink wrap." [Added emphases mine.]

From GM on visual vs. play grading:

"In an ideal world, every record would be played before it is graded. But the time involved makes it impractical...unless otherwise noted, records are visually graded."

*GM about 'Still Sealed' records:

"...let the buyer beware...it's too easy to reseal one...if you're looking for a specific pressing, the only way you can know for sure is to open the record." [I would add that the same thing is true of record condition, because warping/heat damage, as well as defective pressings, cannot be detected through a sealed cover (in fact, the plastic wrap may actually cause warping over time).]

And they state:

"Near Mint is the highest price listed in all Goldmine price guides."

So Elizabeth, "Mint" is not really a standardized, GM-approved description when it gets casually tossed around in ads, whether the 'grading' was done visually or by playing. Most sellers who repeatedly use the Mint designation are not, I think, trying to be dishonest, but rather are probably not 'professional' record dealers or graders. When in doubt, it's better you talk to or email the seller with specific questions, and/or to get them to provide you with a detailed layman's description of everything they can see about the condition of the record in question.

Didn't know your ebay name, sorry for upping the bid on Mingus!! Good thing I stopped by VA today. I'll keep an eye out so as not to do this in the future.