"It does what JCMs were meant to do, just better"

I'd really like to see the day when that nonsense myth is finally laid to rest.  :-(

All weightmapping can do is give you better granularity, which at best allows you to use smaller JCMs. Which, btw, have zero impact on performance. As opposed to a gazillion of joint magnets or additional bones crammed into a cr2.

A weightmap can move a vertice in exactly two directions: In or out in relation to the joint axis.

A JCM can move a vertice into any direction.

So, sorry, unless you have a completely featureless mesh, JCM's were, are and will be absolutely necessary to create an authentic looking human joint, while weightmapping is definitely not.

I rigged figures that bend more realistically than any recent "weightmapped" Poser figures years ago, just using those "primitive" falloff zones and JCM's.

BTW, the "pro's", use them, too. They just call them blendshapes.

I don't know why and how this "JCMs are evil" nonsense started, but it is the reason we now have "professional weightmapping" in Poser and pretty much nothing else to show for.