This is actually pretty common, and depending on which document you read, intentional for at least the the M74. The outer shell was there simply to provide spin for dispersion (google "magnus-lift") and arming - no precision required. It is possible that magnus lift was not providing enough dispersion and it was decided to throw some wobble in as well, I don't know. The document on the M74 says "one shell has two shortened flutes, creating an asymetrical design". This does not seem to be consistent in all cases, but what else is new.
There has always been a certain amount of confusion over the BLU-63 / M74 subs, and I suspect it carries over to the EOD documents. As some of our members can attest, the pubs are are not written by wizards, and while some are pretty decent, many are full of errors or shortcuts.
The M74 / BLU-63 are pretty much the same munition, with the same fuze. One is used from a ground based system (M74 from Lance / ATACMS) the other (BLU-63) from air-delivered dispensers. There are several minor variations of each. The EOD docs give a different explosive though, and they also give a difference in measurements, though I doubt that this is accurate. If you look at the diagrams in the pubs it appears as though they are being measured diagonally, from the right side of a flute on one end to the left side of a flute on the other. Why anyone would measure in that way I don't know. The pubs say 71mm across for the M74 and 76mm for the BLU-63.
I've attached a couple of photos of mine. The left one has all short flutes on one side, the right photo has none.
