preamp inverts polarity

I have a tube preamp that inverts polarity (for some reason it is designed that way).  I reversed the speaker connection on one of the speakers, and it sounded better to me.

Playing a test record confirmed my suspicion.

The catch is:  not all of my records sound better with the speaker wires reversed on one speaker.  I would say 80% of my records sound fine either way (I can't hear a difference), but some (those with good sound staging) have improved "imaging" (if I am using that term correctly).  And a few "image" better the other way.

This makes no sense to me.  Is "phase inversion" the same as "polarity inversion"?  And why do some recordings seem to have it backwards?

And why would anyone want to change both speakers? 

In case anyone is still reading this thread, I need to clarify the end result of my experiments with "phase" and "polarity".

It turned out I had a speaker wire reversed at the amplifier.  Once corrected, I was able to run "stereo polarity tests" that proved my speakers were "in phase" (https://www.audiocheck.net/audiotests_polaritycheck.php).  Also confirmed with my HiFi News test record.

It seems we need some concise definitions regarding "phase" and "polarity".  I have no idea what to call it, but if you get your "red" wires and your "non-red" wires reversed somewhere along the line, you will end up with compromised imaging and sound.