Very helpful. (And why nobody can say this officially now, or could have said it four years ago, I have no idea.)
So in fact what you have here is two requirement levels. STOL for expeditionary operations from an extant runway (the length I have seen most often is 3,000 feet, set by a C-130 for support), and STOVL for ship ops.
There are alternatives for a 3,000-foot runway capability, including giving the Marines the A-10 and (or so I am told) an 800 m-runway supersonic multi-role fighter that is half the size and cost of the F-35B.
For the USMC, the strategic value of VL is limited by ship capacity. The long-term goal is still 11 LHA/LHD decks, each with six F-35s under normal circumstances (although the current number is nine, and the fleet will not reach 11 before 2024).
R&D and the design penalties imposed on the F-35A/C are sunk costs. The future acquisition of the most expensive combat aircraft in current production, and its operating costs, are not. How much are those (theoretical) 66 deck spots worth?