Previous Tor version is in the stable repository for a long time already. However, there is no great transparency when that package was migrated to the stable repository. This is related to packages.debian.org APT package repository web interface for deb.whonix.org.
Uploaded Tor version
tor_0.4.5.9-1~d10.buster+1_amd64.deb
to Whonix stable-proposed-updates repository just now.