You brought some excellent points in this content! One thing you didn't mention regarding the portability aspect of the equation, though, which is my case and the case of many others:
If your out and about workload consists of relatively simple tasks and/or lightweight programs use, and you ALREADY have an old Macbook lying around (whether it's an M1 or, as in my case, an intel-based Macbook), you ALREADY have the portability aspect of your equation. Sure, you will definitely notice the speed difference between your at-home Mac Mini and your out and about Macbook, but if your workload consists anyways of lightweight tasks or if you can reserve heavier workloads/program use when you're back home, it shouldn't be an issue.
I plan on getting an M2 Mac Mini with 512GB SSD (still thinking about whether or not to upgrade to 16GB of RAM), while still holding on to my 2018 Intel i5 Macbook Pro whenever I need to do some med school related work while I'm out and about.
Edit: The value of the M2 Mac Mini vs any M2-based Macbook relies heavily on whether you already have a mouse, keyboard, and - most importantly - a monitor lying around. As mentioned in the content, I'm one of those who used their macbook 90% of time in clamshell mode hooked to a monitor and therefore already had all three of those. I can see how for some people that don't already have those, the Macbooks, especially the Air, can seem like a better deal since it's an all-in-one alternative.