I haven't been on the other end, so I don't have first hand knowledge but it seems to me that it's far easier to dismiss contributions because you didn't make t

I haven't been on the other end, so I don't have first hand knowledge but it seems to me that it's far easier to dismiss contributions because you didn't make them or they don't fit into your careful plan then giving up complete control and cultivate a strong contributor community. All the reasons you ascribe to it aside from "documented" aren't applicable here. The feature was in the bigger vision, it was well tested, backward compatible, etc... The only reason touted for not accepting it is that they wanted to get another feature in first.