Nintendo, like all other platform-owners (e.g. Meta/Quest, Sony, Microsoft) is VERY strict about games released on their platform and have very strict requirements before anything is allowed to be sold with the Nintendo label. I very highly doubt they let devs NOT implement the pause ability. AFAIK you can't just OS-pause a game and expect it to run fine when it resumes, there are soooo many systems at play: animation, physics, sound, input, etc. that need to be cleanly stopped/resumed that I doubt it's as easy as just OS-pausing.

This used to be true, but one trip to any modern e-store front should dispell the notion. So much slop. Even for arguable non-slop, so much that just rapidly crashes and is unplayable. The extent of platform certifying these days for most titles seems to be: can launch, can back out to the console top level, and maybe doesn't crash if a controller is added/removed.