That's exactly how I'm looking at it. I'm pretty optimistic of growing rapidly within the company if/once I take up the offer, but then again, who knows how internal company dynamics actually work!
While I'm at a somewhat decent level at my current position, I don't see growth opportunities, at least in the way I want to grow. I'm wondering if starting again at a lower rung, but hopefully, in the right path, would be worth the "demotion" so to speak.
I hope you're right about the "find that they're not overqualified at all once" bit.