ismodelocked map arg?

Just a small question.
As far as I can see, the command getmodelocked allows to check if a mutator (arg3) is allowed for a given game mode and set of mutators (some muts are mutually exclusive). There's also a fourth argument for a map name, but I don't see how this one works. I thought this might check as well if the given map is allowed. No matter what string argument I try, it does not seem to make a difference. Okay, I can also look up a mapname in (getmaplist $mode $muts), but I'm just curious if this functionality is already included in getmodelocked.
As far as I can see, the command getmodelocked allows to check if a mutator (arg3) is allowed for a given game mode and set of mutators (some muts are mutually exclusive). There's also a fourth argument for a map name, but I don't see how this one works. I thought this might check as well if the given map is allowed. No matter what string argument I try, it does not seem to make a difference. Okay, I can also look up a mapname in (getmaplist $mode $muts), but I'm just curious if this functionality is already included in getmodelocked.