And I know of no NM connectors listed for use with MC.
I agree for MC cable those things are junk also MC-ap requires a connector specifically listed for that type of MC cable. We never used anything but a saddle type connector.Regardless, looks like a cheap way to do things to me.
What the heck? How does that work?
Anti-short bushings are not required for MC cable per the NEC. I still use them (or I prefer a couple wraps of black tape) because it is a better installation.There is no picture where MC cable conductors exit this what appears to be a type NM ( romex ) connector . If it had a full opening there is nothing stopping anti short bushing from falling out ( even armored cable types that anti short bushings are not required always install them ). A few years ago we had a case of garbage made in India 1/2" die cast duplex MC connectors that did not have a listening on what sizes of MC cable they were listed for. We were using them for 10/2 MC cable.