Case Book Situation 10.6.11B adresses "stationary" situations (not moving) similar to this and basically says that it all depends on whether or not 1) B has an opportunity to avoid the contact and, 2) did B use this opportunity.
If A's position is so close B can not avoid contact it is a block. If A's position is such that B had the opportunity to avoid contact and didn't B is charged with the foul.
IMO, it's probably a judgement call I'd have to actually see to make up my mind.
However, it's Fri night and most of the experienced refs are doing V games tonight and I'm sure will chime in when they return.....
