Take a look at any of the "new" releases of Macbooks over the past couple of years, and all the problems that people have with them. From butterfly keyboards, to having to charge through right side to avoid CPU slow down, to all the problems with software in Catalina especially how it breaks features on older Macbooks, e.t.c
IMO anyone who actually gives about tech should have stopped buying Macbooks since they started soldering SSDs into the board.
It makes a lot of technical sense to solder SSDs to the board given the insane speed of modern SSDs. Solder joints are much better than a connector for a high bandwidth link. Even tiny parasitic capacitances become a major headache.
Are they accomplishing anything that couldn't and isn't already done well be an NVMe M.2 connector? All that comes to my mind is a miniscule space savings.
I suspect they are getting better speed and power consumption, and deeper integration with T2 (which functions as the controller chip). Apple is generally ahead of the curve when it comes to SSD performance in laptops, so it's unlikely that a generic SSD connector would function as well.