So effectively you're saying we have two years of delinkage.
No, not at all. You can say the cap will be X, but still make sure that each side will only get 50% + make whole. What it does though is ensure that the players are not getting a massive hit to escrow - which would happen if the cap was too high for revenues. However if revenues are too high for the cap, then the owners all have to chip in to top it off (which has been done twice before).
Really there's no lose here. If the PA wants 65m, then give them 65m. Depending on how the floor is determined, it'll mean small clubs have to pony up a tad, but it's not the end of the world. The 50% split still protects everyone.
Eg: Year 1, cap is 70.2m. Revenue in a shortened season is 2B. PA gets 50% plus 200m in make whole (am just guessing).
Year 2. They have an artificial cap of 64m. Revenue is 3B. PA gets 50% plus 130m in make whole (still guessing - based off the 400m comment).
Year 3 - now based off of year 2 they have a pretty good idea where the yearly revenue should land - so they base the cap off of reality - 3B+growth (say 3-4% to be conservative)+72m in make whole (still guessing). That puts the midpoint around the 53-54m mark (and the cap around the low 60m range depending on how it's determined).
So the cap itself doesn't really matter too much... as long as teams don't spend right to the max between years 2 and 3 - at least until they get an idea where things are revenue wise. The split protects both sides from it rising or falling too much. But the lower the cap, the less of an impact the PA will feel in escrow.