It really makes no difference what you "consider" to be part of the GNU project. The fact is that Glibc is the software you chose to add to. All the code you wrote for it is now held under FSF's exclusive copyright, with your explicit signed approval. Glibc was then and is still unambiguously under FSF management, $&%$& or no. (Eglibc, used in Debian and offshoots, is another story; your code is in there too, and still owned by FSF, but managed by somebody else. You might feel better about working on eglibc.)
The fact is that the Linux kernel would have been useless had there not been a GNU project, already in place, to drop it wholesale into. If Linux had not come along, a newly unencumbered BSD kernel would have been adapted a year or two later, and would since have forked, and would now be managed by mostly the same people as do Linux today -- maybe Linus included. It would, then, have been a GNU/BSD system. The same names would be complaining about that, instead, with arguments of exactly equal merit.