It isn't rust on the taper, but there is an inconsistent finish that looks spotty - still feels smooth to the touch.
Here's another pic with the ball joint shaft at the extreme range of motion... I realize that with pressure on the boot it won't slip off as easily as it has here, but it still doesn't give me a lot of confidence that there isn't enough room for play without pulling the whole boot out of position.
I talked to PST again and they insisted that it's fine... without seeing pictures of it. So I guess if I need a better fitting boot, I'm going to have to find one somewhere else.