Dear Nandric: IMHO only an audio myth ( I mean with heavy mass TT designs. ): not proved theory.
I tested ( posted somewhere at least twice. ) that myth not with one cartridge running but with three cartridges running at the same time with no speed minute changes in different recordings and at different position in the Lps: near the spindle, outer tracks and in the middle.
Even, now that I remember, I made other tests where I changed the cartridge VTF using it at maximum ( on its specs. ), I run too a test with the motor switch-off and even with the platter with out " belt/thread " to test its time to stop.
I really made several tests, for different reasons, and the cartridge drag when in playback did not showed influence. Where I detected influence was with out motor/belt and even differences ( tiny tiny very tiny ) due to a diffrent cartridge stylus shape and VTF.
Regards and enjoy the music,
Raul.