Yep, I found that odd too that Don didn't list "photo courtesy of Carl". Though perhaps the engine changed hands at some point? My other one runs good without the stabilizer but it has bent over slightly, which I think that is what that plate is really for but I don't want to put one on because it didn't come it with.
I also find it interesting how the made the upper brace opened on the inside and then closed later on (required on a B30 for the pulley), with those they have the added slip rings to completely stop the side to side movement. You'd figured they would have done that from the start.