iFixit opened up Apple’s new MacBook Air and Mac Mini and there are some notable changes to the assembly methods of each. The Mini now has user-replaceable RAM, reversing Apple’s decision in 2014 to solder it directly to the board, while the Air differs from recent MacBook Pro models by allowing the battery to be replaced independently of the top case.
Yes, storage is still mounted directly on the logic board, but it’s understandable from a security perspective — it is closely linked to the T2’s hardware encryption. (See update below.) Overall, these are small but welcome improvements to repair-averse recent production techniques.
Update: It doesn’t appear that the security features of the T2 necessarily prevent a Mac from having changeable internal storage — at least, not according to the security guide and, more tellingly, iFixit’s teardown of the iMac Pro.