My explanation for that would be, 1. The B1G is the bomb, and they are on top of it for now, having defeated everybody (sweeping at PSU, splitting H&H with UW, handling MN, two over MSU, @ Purdue). The B1G has an unbalanced schedule, so only ranked opp will be Purdue at home, and then tOSU once the rest of the way, besides helpings of Mland, Rutgers, NW, etc, so the RPI will drop a little. 2. The losses (at Fla, neutral Oregon) were without their starting AA setter. Of course nearly everybody else has a similar injury story to relate as well. The WTF loss was in four sets to UNI in Omaha (a definite tourney team).
They have no margin of error IMO to finish in top 4. I think Penn State can lose one more (at UW) and stay up in top 4.
Stanford lost twice to Penn State (though likely NPOY Plummer was not well/sick in those matches). They are pretty much dominating a very very deep Pac 12, which doesn't have any other elite teams, as U-Dub has had tons of injuries. Otherwise, it's kind of a RPI heavy top 10. I would expect Fla. to rise into the top 4.