I'm pretty sure it's the same plant :-) Photos of A.p. 'Mirte' and Talon's 'Mirte' look pretty much identical. I can see why the assumption is to include as a shirasawanum - quite full leaf shape characteristic of that grouping - but it is also characteristic of the Matsumurae grouping of palmatums, with which it is most typically included.

I know there is often some confusion or shuffling between palmatums and the japonicums/shirasawanums, but other than Talon Buchholz, I could find no one else that includes this cultivar as a full moon maple. And that includes F.C. Esveld, responsible for its introduction.