I’d be fully onboard with bi-generation, if instead they had explained it happening because of the Toymakers abilities to mess with the laws of physics. I’m surprised they didn’t go that route.
EDIT: I’ve been reading people talk about this idea on other social media platforms. I bet eventually RTD will confirm this. The bi-generation was a myth but the Toymakers powers did indeed bend the laws of the universe and make the myth a reality.
I’m thinking it might be a natural thing for the Doctor. While I wasn’t watching for a while, I’ve caught bits and pieces of the Timeless Child, which IIRC is the Doctor and he’s not actually Gallifrean? So maybe things are different for him, plus this explains the Curator and the Renegade Doctor.