They are in different areas, and at this point, each ship is basing their protocols on what is happening on their ship.
Example: Majestic is in Australia, has 800 cases, so they are having enhanced cleaning, mandatory masking for crew and passengers, etc. as well as mandatory testing per the area that they are in.
Regal is in the Med, has very few if any cases, so there may well be no mandatory masking for anyone, normal cleaning, and no mandated testing unless symptomatic, per the Master of the vessel.