Or because other people in this thread insist that in fact it's not stable, and there are numerous bugs on multiple platforms.

I don't know what plugins those people use. They might have thrown in the kitchen sink of unstable plugins. Lots of people using ST3 in the forums without issues. Plus I know my personal experience on my platform of choice.

Regardless, if you want people to know that a release is ready for use by people who want a stable release, you label it a final release, right?

Well, some projects prefer the perpetual beta designation. Heck, even Google did that for years for stuff like Gmail etc.