Right, I agree with you that where the business is incorporated has essentially zero bearing on where its HQ is, where it can operate, hire staff, etc.

But I think that it counts for a little bit more than just "details for your finance person", since the tax and grant eligibility implications could mean that some startups would be better off incorporating in Canada and not taking the Y Combinator money. But if you're taking the VC funding route (which most applicants to Y Combinator are), then I agree that none of this should really matter very much.