I don't think it's much of a showstopper either. Not having a "universally agreed upon definition for the words AGI, consciousness or intelligence" haven't prevented us from considering other people conscious and intelligent, or animals conscious, etc. It wouldn't preclude us considering an alien race coming to earth as conscious and intelligent either.

Sort of how we didn't have a "clear definition" of most things for millenia, but we still were able to recognize them as a class of thing. It's more of a "I'll know it when I see it" kind of thing.

And the external behaviors (of consciousness and intelligence) matter more than "but is it really conscious/intelligent inside" when considering some AGI as such. After all we neither can clearly define, not we know or can measure what's going on inside another person's head regarding consciousness, or to be frank, not even on our own head. When it comes to us, we just have a subjective experience, and not even a very clear one at that.