How do you prove that you’ve met the minimum stay requirements under the Portuguese Golden Visa?

I have only used boarding passes showing entry and exit and have had zero problem with renewals.

exactly! It is also my experience on this issue

My recommendation is on the contrary, I believe it is worth obtaining the NIF for each GV dependant including minors. Makes everything easier while in PT.
Since 2022 there is no more mandatory tax rep requirements/extra costs.
I cannot see any possible negative consequences of having a NIF.
NIF does NOT equate to the tax residence either.

What exactly does Nif make things easier for visitors in Portugal? I cannot see any…