Are Giottos Mh-621 and Manfrotto 501PL compatible?

From what I can discover by reading the reviews on B&H, it is compatible with the Manfrotto 357 QR adapter, which does not take the 501PL plates, but 357 plates.

In fact it looks like a complete rip off of the 357 but with a few bells and whistles added.

So, from my investigation, no.


CS