HI
I also find the same symptom in FSLogix_Apps_2.9.7654.46150 this new version like picture.
"Does that mean it does not need to be enabled for Citrix/RDS servers anymore or should i just enable through the registry?"
I think if we want to use "Allow concurrent user sessions" policy ,we can try to enable it in registry.
there is a document for your reference.
Configure Profile Container and Office for concurrent connections and multiple connections
https://learn.microsoft.com/en-us/fslogix/configure-concurrent-multiple-connections-ht