I think, (heavy on the think part!), they did put the 351M in the early Bullnose Broncos. Good point, that could cause the confusion.
I shouldn't be cynical, "Cleveland" is one of those buzz words people like to use.
Same as most of the Ford "Highboys" magically have 390 engines in them. It's my understanding Ford never put anything bigger than the 360 (externally identical to the 390) in the "Highboys".
Alas, I'm no expert at all, and should not let these things bug me!