Hmm, yes that is interesting.
Perhaps it's for roughly the same reason that the first CVF will be a STOVL carrier; i.e contract and materiel already being worked on. Lockheed Martin are already in the process of building 2 STOVL jets for the UK in the LRIP 3 run so it was probably too late to switch to a F35C on this contract given our announcement to change variant only 4 weeks ago. UK needs these jets for operational testing and I imagine F35Bs will still meet the bill for mission systems testing vice being needed for STOVL-unique which is now moot for UK.
I would bet our next order is for an F35C just like the next order for HMS Prince of Wales will be for Cats and Traps.
Just my opinion.