Always have been the same, and probably not changeable based on how an owner purchased. That would require approval by RCI and I doubt they'd agree to anything which would reduce DVC exchange inventory.
As Bill said above, DVC could change the rules for everybody, change exchange companies, or eliminate exchanges altogether. But they recently signed another contract with RCI that has 4-5 years to run, I believe.
For those who don't know, DVC/RCI options were greatly expanded a few months ago and now include the vast majority of RCI-affiliated resorts. Far more choices that the previous <600 resorts.