I would much prefer to see Thunderbird updated early in
Rawhide and releases that are not yet final, but to remain on the older
stable version for as long as possible on any Fedora release that had
included it.

That'd be a problem though because ~every Thunderbird x.y.0 release
includes security fixes, which are not backported to older then
unmaintained ESR releases by Mozilla.

I don't understand... When I said that I'd prefer to see Fedora remain on the older stable version "for as long as possible", I meant "for as long as Mozilla continues publishing security fixes for that release", which should be at least 12 weeks after a new stable release series (x.y.0) starts.