The point of allowing ports to the current version is to ensure any content, should a person be willing to put the effort through to port it, can be played on the current version that the vast majority of people play on in the first place. Allowing people to port stuff to other versions makes things a far bigger pain both for the Judges, as well as the average user, and doesn't have much purpose in the end. If you're going to port a version, why not the most recent one given it has the most features available to make use of anyway.
Regarding taking mods from 2.2 to 2.1, that's just making a worse version of the mod generally to not much benefit as much as I think demakes are pretty interesting it's full on modifying someone's elses work for no real reason but because.