How does Weapon Bias work in MH4U?

In MH4U, registered guild quests have a "Weapon Bias". What does this do? (By registered guild quests, I mean the guild quests you obtain randomly which must be manually registered in order to undertake them, level up each time you do them, and can be transferred to other players).

Does it mean the drop rates for that kind of gear are better?

If it does, can you still find other kinds of gear in the Everwood during that quest, or just the types listed in the bias?

The Equipment Bias affects the drop rates of rusted items. I have gotten multiple items of the same type in the same quest, and they matched up with the Equipment Bias.

I have done these a few times now, having obtained ~10 rusted pieces (at work so I don't have an exact number). None of these pieces were different than what was shown in the Equipment Bias.