It does say no airborne flight plans, which (if the RA is treated as CAS) means no flight, VFR or IFR, unless a written flight plan is submitted.
That's what the website says, anyway.
They may well relax it later to "radio contact required" which would make sense because it would deliver the same "known traffic environment" which is all this can be possibly about anyway. They want to be able to spot unknown radar returns ASAP.