No. The Player groups that are the by default always return and use the same value AFAIK.
Additionally Player groups don't leak if the reference is never lost, same with all other leaks too like locations.
Generally speaking the leaks are only there when a reference to something is lost and not cleared.
Example:
Setvariable AlliedTeam = Players 1,2,3,4
Pick every player in AlliedTeam
do actions
Then if you don't want to ever use this gain you need to destroy the playergroup before setting AlliedTeam into a new value.
Because if we then made:
Setvariable AlliedTeam = Players 5,6,7,8
The first made player group of 1,2,3,4 would not have reference anymore and it would then leak.