As others have explained in the mailing list, the technical ability to dump the AST in a way that circumvents the GPL already exists via GCC plugins. So, no, it doesn't make sense even from that perspective.
I guess it makes sense to RMS, but his brain is a very strange place.
It makes sense in the context cited in TFA.
RMS would rather go down in flames than risk having third parties "abuse" GCC.
Substantive evidence that the situation has changed since the founding of GNU is moot.
RMS's binary view is arguably unfortunate, but there it is.
He's painted into a corner by ideology. He can't get any more flexible than he already has.