It's not user-replaceable. It would not be _that_ difficult for Apple to keep a SODIMM slot free, or even come up with a new standard - as they are wont to do.
Apple sacrificed upgradability in the name of making more money - it's as simple as that.
Considering even the Ryzen 7950x or Intel I9 for desktops are 128 bit wide that's a pretty huge difference. You have to move up to Epyc, Threadripper, Xeon, or a Workstation CPU to get more than 128 bits, and those aren't available on laptops.
So I'm going to have to disagree with the "Apple sacrificed upgradability in the name of making more money".
Well, it's not because Apple doesn't give access to parts, otherwise it would be.
Not sure how use of hot air station suddenly makes it something that a user can't do?
You can buy a hot air station for less than $100 and it will do the job. Only caveat is that the replacement part needs to be new (so it has pre-applied solder balls) - otherwise you'd need to reball which a bit more difficult, but not something that can't be done at home.