In the demo images and videos, they appear to use the OF-2200 without collection on the tool itself, just on the mill mount. I would have assumed that meant that the mounted collection was adequate to keep up with the router (to the extent that any collection can, really).
I can't imagine that you would see enough additional collection to justify the complication of a second set of Y adapters just to combine the mounted collection with the on-tool port.
Have you tried it out to see if the collection is adequate without on-tool collection?
I would think you'd be better off whipping out a Festool CT and connecting it to the tool in parallel with the dust collector rather than trying to split the hose a second time, personally.