Usually those that they recommend are official versions that they support, which means they can give support for those versions, and they know it’s working.
You could use a version that is not in the list, but you might run the rist of compatibility issues with SignalR and other libraries and the EC team can’t guarantee support to assist you.
But since the new submission process, you have the ability to control your bot’s building process, which means you can change versions to your liking.
Just remember to adjust the correct files, such as you project settings and Dockerfile to use the same version as well.
A big risk with untested, unofficial versions is that if something goes wrong during a tournament, you will be at fault for not using the recommended version, and the tournament will stay as is.
Where as if something goes wrong with your bot using the official version, it’s up to EC to fix it, and rerun the tournament.