This is bad. Because,
a. Switch 2 can get bricked when Nintendo wants you to upgrade to the “Switch Tree.”
b. If you discover a purely unused switch 2 decades later it will be useless. It’s bricked unless you get that Switch 2 update.
c. It all ties to that Nintendo bricking terms of service terms.
Good question. I always assumed the updates were cumulative (as in, a later version would contain anything needed from older versions) and that pretty much every cartridge required some firmware that was newish at time of release… such that yeah, each cart would have a version of firmware update on there.
But there are a lot of assumptions on my part there. And the Switch 2 situation could be a totally different kind of thing for all we know.