Ah, totally missed that, my bad.

It’s amazing that this is said almost every time someone talks about mortgages and interest. The vast majority of mortgages are not simple interest - I think people get used to it being that way with car loans and then assume it’s the same with their mortgage.

Your last points are only true if you have a simple interest note, which the majority of mortgages are not. Most mortgages you pay the same amount of interest no matter when you pay it, except at payoff. The only thing that changes that is contributing additional to principal. The calculation for interest paid with each monthly payment is simply rate times UPB divided by 12.