If grens needed to be nerfed because they were too strong against cons, you wouldnt nerf cons simultaneously, you would just nerf the grens.
If TDs are making it too difficult to utilize heavier tanks like the panther and thus need nerfs, you dont nerf the panther and thus defeat the purpose of nerfing the TDs.
The purpose of nerfing the TD, I have always been assured by those who suggest nerfing them, is to reduce their effectiveness versus Axis medium tanks like the Panzer IV.
On the other hand, the reason allied TDs are so good in the first place, and so ubiquitous, is the fact that Allied MTs are incapable of fighting anything heavier than a Panzer IV period anyway, and every Axis faction happens to have such a vehicle stock in their roster; the Panther, which is perfectly capable of fighting one on one every stock allied tank short of maybe the Comet (on a good day RNG-wise, favoring the comet.)
So if we are to improve the medium tank game for one side of the aisle we might as well do it for the other, because I can tell you right now that if allied TDs get nerfed, its not going to stop you from seeing them nearly every single game, because there is more often than not no other way to deal with the heavily armored Axis tanks that are almost assured to appear.
If you think the TDs need nerfs because they are too good versus the Panther, you're bloody insane, since I don't know what else you expect to see countering it.