It is and I am sure.
There is no "standard" for Meucci collars (which is an unfortunate problem b/c most CF shafts don't line up), nor buttplates either (which are sometimes way too wide for my liking).
I have owned many Meuccis (most of which I sold now) and the collar diameters are all over the place. I have an original OL-1 with a 20.15mm collar (and had others pretty close) so they do come pretty narrow sometimes. The Kevin Cheng BMC cue that has been my main player last few years is 20.5mm. The current Meuccis seem to average wider but I don't play with them.
If you don't care about the ring pattern I can take a look if I have another shaft with your diameter (or wider which can be machined down). I kept several Meucci maple shafts for backup but I switched to the Cynergy shaft and don't really play with maple anymore so I may get rid of some more.