Conspiracy Theory
Being very cynical and looking for a conspiracy theory (devious senior RAF having over gullible RN again), could the advantage of the F-35B that it will enable the RAF to retain primacy as the aircraft need only pay fleeting visits to the carriers, whereas the F-35C will need them to spend a significantly greater time afloat thus giving the FAA an opportunity to again have a significant role in fixed wing operations. Just a thought, please don’t be too rude to me!