What the heck are you talking about, putting that on Bell? Referencing the first couple seconds of the video, it wasn't flopping, Allen whacked Bell in the head with his left elbow, possibly his right wrist too.
5 or 10 seconds before the video starts, Bell had position under the basket, and Allen got into a crouch and drove his entire body into Bells gut to move him, combined with a couple more intentional hard blows to the head. No foul called. Did the Celtics blog say that those hits were flops too?
You try playing sharp defense 3 seconds after whoozy from taking a shot to the gut and 3 or 4 blows to the head. 5 point swing there, determining rebound and open 3 pointer.
Celtics got more calls all game, and yet the refs spent half the 4th quarter listening to Doc Rivers sob. I think one ref was ready to give Doc a hug and buy him a beer. So they spent the last 5 minutes looking for what Doc and other Celtics told them to look for, and looking for every opportunity to give "make up calls" to help the Celtics even more.