Not a Boffin,
That's a new one to me - I'm not convinced that the RAF gave a huge amount of consideration to survival of the Harrier Force (and a successor Harrier Force); more that the F-35B wasn't a direct competitor to DPOC (FOAC then FOAS then DPOC.)
F-35C was. Keep the STOVL variant, keep another manned aircraft flown exclusively by the RAF alive.
Choose F-35C, take the risk that not only was 50% of the Force to be flown by the RN, the F-35C would be a very strong competitor and tick sufficient/all the DPOC requirement boxes.
So DPOC = F-35C and, saints alive, it can be flown from sea.
Knowing that the UK was flush for expensive aircraft and that at least 1 defence review was going to happen between then and final variant slection, survival of the Tornado Force follow-on was more likely the motivation.
I wonder how many senior officers in one of our services will ever refer to the F-35C as a 'Carrier Variant'? Not many.