Ah, I now see what you mean, and I agree - it's a bug.
I misunderstood the issue and was holding 12 notes at once, and then seeing the behaviour on adding the 13th, but that is not the issue.
In 'Reassign', playing 12 notes one after each other, *without* holding the keys i.e. staccato, it stops playing after it has sounded 12 notes. All voices have definitely finished sounding, but it will not free up voices. It will only 'revoice' previously played notes.
That's not how 'Reassign' is meant to work, and not as described in the Arturia Manual.
cheers Jeff