TD's story concerns current 55th Wing V/Ws. Any whistleblower would have to be terribly old to remember RC-135Cs and Ms.
The ancient, clapped out R model tankers that we're getting may be even more problematic. Can you even imagine how clapped they must be, given the shortage of Rs, if the USAF parked them in the desert?
The three aircraft were the last 3 KC-135As off the production line, 64-14827, 64-14828, and 64-14829. They were converted to KC-135R standards in the 1980s.
They will be redesignated as RKC-135Rs while undergoing conversion (to V/W standards), and reportedly as RC-135Ks when delivered to the RAF. The RAF serials will be ZR135, ZR136 and ZR137, but not necessarily in USAF serial order. More information that I don't need to know.....
Your pictures show an RC-135V (about Baseline 7) and a Baseline 10 RC-135W. This demonstrates the fact that, like the Nimrod Rs, the Rivet Joints have had a frequent upgrade cycle, and not a one-step upgrade. I would suggest that your linked source is a bit 'noddy' since it doesn't even mention the Baseline standards.