There are ~2 strings using the wording of "Group Plus", while the rest of the game goes with "Group+". No other instance type uses the "... Plus" version, only Group ones.

There's no reason to keep using both, it's inconsistent. The same case as with "VRChat+" and "VRChat Plus" that got fixed.

"Group Plus" should be replaced with "Group+", just as "Invite+" is never referenced to as "Invite Plus".

Moreover, most translators still go with "Group+" as the accepted translation for "Group Plus" either way. (screenshots)