I suspect it was due to how sometimes the game will frell up the chosen difficulty setting if the team lead isn't in zone before someone hops into the mission. Although, the game drops to +0 when that happens. Some folks do like -1 for speed runs but if that wasn't also part of the deal, I don't know what the leader was thinking.
For me, it seems like most problems can usually be avoided if the team lead is fully up front during recruitment. If I'm feeling up to running a PUG ITF, I'll always broadcast Max Diff ITF Kill Most lookin for more. It's when folks start whining halfway through first mission that it's too hard that I get annoyed. Max Diff means +4/x8! If ya can't handle the faceplants, ya should have brought a better build.