It's not semver (that'd put them on, IDK, 4.something maybe) but the versions before the first dot still signifies "significant" to me which this is not.

That's not rolling release, that's still a form of stable releases. You'll get the feature set of 117 for a month or so with important bugfixes backported from fresher branches. If that ain't stable, IDK what is. The only truly rolling release of Firefox is Nightly.