I have seen this tool. I thought it was to hold the camshafts in position when the belts are being removed. You are saying this will secure the camshaft so the pulleys can be removed?
The honest answer is that I don't know but it looks like the only factory tool that comes close to properly locking the camshafts out. How well it does that job is debatable looking at the way it's retained. I don't know if you've got a copy of the factory manual but the one I found didn't refer to any specific method at all. It showed the cylinder head in a vice/stand and just said remove the outer caps and undo the bolts (tightened to 90nm!). Sometimes factory manuals can be frustrating brief and overlook the really obvious question (s).
Call the dealer who did the Desmo service. Any reasonable workshop would not bemoan giving you some technical advice and they do have a degree of responsibility as they were the last to work on your bike.
Yes, I have read through the manual several times and cannot find a simple explanation. I have managed to get it off by and old cam belt and ratchet method.
