You need to buy a ML tag if you ever want to use the crossbow for hunting. Period
The Either Sex tag can be used during bow season with bow or later part with crossbow or in the late season with Muzzleloader.
Crossbow use is usually after Nov 1 and you can use it to fill any of your tags of that season.
For example if i used a bow or crossbow during regular gun season, I would put my reg season tag on the deer although I used a bow or crossbow.