From personal experience, it seems like it might be in your head. A green speed is a green speed. Now WGT may "tweak" them from time to time after an update, but I've never noticed it from game to game based on who's playing. I have noticed my calculations for a 13 green before an update might be slightly off after the update, but it's an "across-the-board" change.
I play quite often with TCs all the way down to TMs, and the calculations don't change game to game for a 10 foot putt 2 inches downhill based on who I'm playing against. If a putt drops in at perfect speed against a TL and goes 3 feet past/offline against a TC you likely misread the second a little, or there was some weird stuff going on with elevation between the ball and hole with the TC (might show 10', -2", but in reality it's -6" for the first 8' but then rises 4" at 2' from the hole).
I also think the lower the tier, the more forgiveness and precision they get. Meaning if I play a Legend and I'm a Champ, we both have the same ball/putter and exact same putt, the Legend might be able to get away with a slight misread or misding, whereas I might not. The game expects me to be "better" and not make that mistake so will punish me more for it. You can call it "making the hole bigger" or whatever. That part I do believe exists, the rest not so much.