The website shows what appears to be a flange on it which is supposed to prevent it form moving toward the seal.

 

A flange on the bushing? I don't really see the need. The pump cover has a land, that will prevent the bushing from doing so. Thats why you have to remove the pump and remove the pump cover to R&R the bushing. I can't say that I have ever had a pump bushing walk out on me, and I have done lots of these trannys.