Guido indicated on python-dev that he considered it reasonable to view adding gi_yieldfrom as part of the PEP 492 implementation: https://mail.python.org/pipermail/python-dev/2015-June/140498.html

That perspective makes sense to me as well, since it preserves the functional equivalence of native coroutines (cr_await) and generator based coroutines (gi_yieldfrom) from a state introspection perspective.

I've added Larry to the nosy list here to give him the option of veto'ing as release manager, but I think we want both in order to get full debuggability benefits.