Don't know, I'll check the code. Did you try unchecking it? Wouldn't be the first time I messed up True and False...
I promise this will be fixed in Arena Match 1.1 (it works in my current internal version)
New features in Arena Match 1.1 (release date: soon)
- working Unlimited Ammo mode
- cleaned up the menu code; menus stay on the screen (try the U4eTWeapons.int, all 65 weapons from Unreal 4ever Tournament with class weapons)
- weapon groups; weapons can be sorted via the .int files (not just by package)
- new Low Ammo mode (someone please suggest a better name for this); pickup ammo amount is the same like in non-arena matches (e.g. 12 rockets in a rocket pack, 6 rockets in a rocket launcher), but you start with full (or even unlimited) ammo
- maybe .int files for other weapon mods (only those not declaring their weapons via .int files)