Though OS packaging may frequently obscure this because OS packagers break up the language distribution, Idle is part of the language distribution, so (unless you expand the distribution to include core packages outside of stdlib, as with Ruby’s gemification effort) it has to be built with stdlib alone. Tkinter, therefore, needs to be part of stdlib.

Taking IDLE outside of the standard distribution and make a separate download link for it, isn't in anyway going to hurt Python at this point.

Just move tkinter like what they do with typing package is good enough to address everyone's need.

Depends, do you consider IDLE part of the standard library? (it's separated in many distributions, but documented in the standard library documentation, so it's a bit mixed, but it's probably okay to not consider it part of the library, but just the standard distribution)