Rocky 10 has SpamAssassin 4 so may be better for you to possibly think about using that instead of Rocky 9. As for SIG’s, you have to remember the team is not huge. So every single SIG request means someone has to manage it. There are only so many people and so many hours in a day. So it would mean someone would have to be willing to take on that extra work and maintain it.
It’s very easy to download a Fedora source rpm, and build this with mock. The Fedora 41 or 42 rpm should build fine on Rocky 9: SpamAssassin Fedora source rpm and this post documents how I did similar with Audacity: How do I install this on Rocky Linux 8? - #13 by iwalker you can adapt some of the commands there for Rocky 9 and EPEL 9 to do it.