The RAF’s selection of a degraded tanker means it can only refuel other aircraft using the drogue-and-boom system,
and so cannot refuel most US combat and support aircraft.
Without searching for and reading the full article, I'm assuming there's more after that sentence. Otherwise I'd have to ask the author whether they think the role of the RAF AAR fleet is to only support other nations' aircraft.
That said, and I might well be imagining this, but I'm sure I once saw a video somewhere of a boom equipped aircraft that had been modified with a drogue element at the end of the boom for probe/drogue ops. Would that be a potential solution? We've spent so much on these damned Voyagers that we may as well spend a little more if it means we actually get the full capability from all our fleets.