There is no question that stylus drag does cause speed variations. The only question is if the variations are large enough to be audible. Our ears are remarkably sensitive to extraordinarily small errors in the time domain. With digital audio it has been well documented that tens of pico-seconds of jitter is easily heard. That seems vastly too small to be heard, but yet it is. With analog it is no different. Very subtle changes anywhere in the drive system are easily heard. Different belts, pulleys and even component quality in the electronics all make a notable difference in the sound. If capacitor quality can be heard in a motor regulator circuit (and it can) then it's not much of a stretch to imagine that stylus drag would also be audible.
Regardless of the theory, what is indisputable is the fact that many techniques targeted to reduce the effects of stylus drag produce audible, positive results. Stylus drag may or may not be the culprit for audible degradations that we all hear but to me it seems like the most logical explanation. It is imprudent to categorically dismiss stylus drag without evidence.
Platter mass cannot reduce the effects of stylus drag. A massive platter makes speed variation shallower but also spreads it out over a longer period of time. So the speed variation is really of the same magnitude but has a different distribution.
Regardless of the theory, what is indisputable is the fact that many techniques targeted to reduce the effects of stylus drag produce audible, positive results. Stylus drag may or may not be the culprit for audible degradations that we all hear but to me it seems like the most logical explanation. It is imprudent to categorically dismiss stylus drag without evidence.
Platter mass cannot reduce the effects of stylus drag. A massive platter makes speed variation shallower but also spreads it out over a longer period of time. So the speed variation is really of the same magnitude but has a different distribution.