When the plinth is made of different materials, such as seen in the SL1000 or the Pioneer Exclusive P3, colorations can be introduced.
To understand this, imagine that the arm board is heavily damped in the way that most audiophiles like to hear and read about. But the part of the turntable supporting the platter bearing is not. What this means is the the platter, when subjected to vibration from whatever source, now has induced motion that is different from that present at the base of the tone arm (which is likely a lot less). So a microscopic difference between the two exists. Of course the groove of the LP has a microscopic aspect too!
So when you see a really nice turntable which is mounted to wood, obsidian, panzerholz or other material that does not include both the platter bearing and the tonearm base in the same assembly, you instantly know a coloration exists.
Now there are aftermarket plinths for machines like the Technics SP-10, but if they don't have you removing the motor from the original mini-plinth of that machine and installing it to the improved plinth, its likely that such a plinth is still introducing coloration although it might sound quite a lot better than the stock configuration.
This is a strength of the SL1200G because its plinth includes the platter bearing mount (the motor in this case) and the base of the tonearm. The plinth is also damped, fulfilling the other requirement for a good plinth.