Thread:Deathstalker666/@comment-1915529-20140221183807/@comment-1496755-20140624211604

The extra ammo is to compensate for the increased speed the of monsters and their projectiles. I think Doom does the same on Nightmare difficulty (although it also features respawning monsters). Indeed, after getting used to playing on BP, you will probably think monsters are very sluggish on Smitemeister (the equivalent to Doom's "Ultra-violence" difficulty). The reduced ammo pickups can make certain level a little more challenging, though (especially E4M1).

Despite this little bonus, Black Plague still is the highest difficulty, so don't worry - you are on the right track.