Give definitive evidence that soldered is faster, in my experience with decent contact this is not true at all. I think the general confusion is around typical ram sticks with a controller onboard and much fewer io broke out compared to the raw ram without controller which is often what you get soldered, with more io broken out.

The bga socket you chose is more for test or industrial hardware, versus desktop cpu sockets which are much slimmer and consumer friendly.

Really disingenuous, imo. It's absolutely possible for Apple to make these chips replaceable, using the heat spreader as the retaining plate.