Celebrity is part of RC so they recognized my RC Status when I booked on Celebrity. I have more nights on RC through the years, but they do not count my upcoming nights on Celebrity towards the RC program.
Honestly though, the loyalty programs are not a draw to me. A bottle of sparkling wine that I won’t drink, or a 10% discount on an overpriced magnet in the gift shop won’t sway me. If they offered a free meal in Specialty dining it probably would.