The whole cycle of rebirth is touched on in the magic crash course in Alon's route, which also has hints of a past connection between Luke and Alon, so maaybe play that route again to see if you can answer your own questions on the reread.
And v47 does mark the end of Alon's route...hence the quite drastic menu changes upon completion.
And...everyone in Shelter is focused on preserving their freedom, and everyone else is too focused on cross-species conflict to care. That is, if they even know humans exist, let alone what they really are.
For most, I imagine they just take it for granted. For them, this is how the world has always been. If they dig, they're only met with insanity, when they're missing the key component to seeing the Truth.
Burry's whole arc was learning to do things for himself...he never wanted the knowledge, he just wanted to make his superiors proud-- then subsequently, to bring his brothers back. Why would he want to look back at this point when he has everything he ever wanted?
But above all, and this is established pretty early on in all routes, most canines are, by nature, dumb (and horny but that's besides the point). It's only through absorbing human mana that they could begin to have these complex thought processes that might lead them to any sort of conclusion for these big questions....yknow, if it didn't drive them mad whenever they tried to use it.
I think the only character we've seen even interested in finding out the history of their world is Alon, but, being who he is, he's definitely an exception.
Also, respectfully disagree on the music thing. Sic 'em, Freedom, and White Wolf are all playlist worthy imo.