Speaking of NUT, it would appear that a base of FreeBSD 13.2 will de facto have version 2.8.1. (And hence, TrueNAS Core 13.0-U6? Or will that still be based on FreeBSD 13.1?)
Version 2.8.0 (the iteration after the long-tooth 2.7.4, which we're using right now) was released in April 2022, which coincides around the same time of FreeBSD 13.1-RELEASE and TrueNAS Core 13.0-RELEASE. So it was probably a sheer unfortunate luck of "just missed the bus".
Other than ZFS, I don't think there's much of the underlying base system that iX version freezes or backports.