What you say is really interesting.That’s a hard one. Could be both G or A. But if I have to pick one it would be A. So bVII-I
I believe there is a certain ambiguity related to the fact that both chords have essentially the same "weight". So while I hear the tonal center to be A, it does not surprise me that others can be hesitant or hear G as the tonal center.
In some sense, this is an harmonic analog to visual illusion of pictures in which people see different things, like the one below in which some people see a young woman and others an old one.
