No, not a joint exercise. M51 just seems to pop up anyplace it wants to, there is no telling what freq it might show up on next.
As far as the Sat 750 and the freq as 8992, the cf of the CW is 8993, but if you are listening in USB or CW-USB mode then you have to offset the tuned freq from the transmitted freq by the pitch that you want the CW to sound at. So, if the CW is 8993 and you are tuned to 8992 in USB mode the CW pitch will be 1000 Hz. This is pretty normal and common for many receivers when listening to CW in an SSB mode, including ones that cost a good bit more than the 750.
T!