Interesting. They must have changed something with one of the chucks.
I have 2 VM120s. one is old and one I got a few years ago, all the jaws I have for those fit both chuck bodies.
I have 1 VM100 from a few years ago.
The jaws I have for my VM100 and VM120 are different from each other, the 100 jaws don't fit on the 120 and vice-versa.
Both the registration ring and the hole spacing are different.
VM120 jaw top, VM100 jaw bottom.
I'm not trying to disagree or argue, but I am genuinely interested if there is a different version of the 100 or 120 chuck body than what I have that would allow interchanging their jaws...