Hmm, I've never needed a knife for any of those three tasks, but then all I've ever dressed is deer and elk. One good blow with my hatchet and the pelvis is separated, and I've always cut the cruciate ligament and snapped the joint free to separate the leg joints. It is a lot quicker and a lot less work according to the butcher. Necks take a few blows with the hatchet and maybe a little knife work to get the tendons free.

I suppose it depends on what you are taught. It sure is handy to know how to do it all with just one blade if need be. I am sure a saw will get the job done just as well.