so why do you think the regional A-cat fleet is distancing themselves from EMSA events? Do they have different needs than the rest of the multihulls attending?

From what little I know of the A-cat fleet, they use similar W/L courses, and while they don't have a spin, they are certainly similar in performance to some (but not all) other fleets. Their boat logistics (setup, trailer, etc) are similar, so the beach/launch areas would be similar as well

Having their own start seems logical, but I suspect that's still not enough to keep their interest in non-exclusive events?

Conversely, is the A-cat fleet using better venues than some of the established EMSA sites? Would they welcome non-A-catters to some of their regattas if there were RC/PRO assistance from those non-a-cat fleets?