For USAU players, and anyone interested in comparing, here are the relevant USAU rules (best I could find):

H. It is the responsibility of all players to avoid contact in every way possible

H.2. Contact resulting from adjacent opposing players simultaneously vying for the same unoccupied position, is not in itself a foul.

H.3.C. blocking fouls

H.3.C.1. When the disc is in the air a player may not move in a manner solely to prevent an opponent from taking an unoccupied path to the disc and any resulting non-incidental contact is a foul on the blocking player which is treated like a receiving foul

H.3.C.2. A player may not take a position that is unavoidable by a moving opponent when time, distance, and line of sight are considered . Non-incidental contact resulting from taking such a position is a foul on the blocking player.

Very similar, although it looks to me that WFDF's "indirect foul" is a bit more strict than USAU's H.3.C.1, which applies only if the defender moves solely to prevent an opponent from taking an unoccupied path to the disc.

Also, H.3.C.2 is, as gfshoexc notes, routinely violated in the upper level college and high level club game in the US. The rule as it's practiced, in my experience, is more like:

"A defender may take a position that is unavoidable by a moving opponent so long as he is set in that position before the offensive player reaches the position."

(Kind of like the charge rule in basketball)