The other angle I haven't seen suggested here is that this is a forward-looking insurance play from Horner. At the moment RBPT are winning off the back of development work done by Honda in previous years. Nonetheless, they are new to the engine game and there is likely some substantial concern that when the next engine regs come they will be left floundering.

By backing the equalisation they give themselves precedent to demand the same again a few years down the line if RB engines fall behind the pack. They are likely very confident in the rest of their current package, to the point that they can risk making the current situation more competitive in order to guard against future disaster.

I don't especially like Horner, but I think it's hard to argue that he's anything but an excellent team principle, possibly the best on the grid. If he's doing this there is zero chance it's for altruistic reasons - there is a play for RB here somewhere, it's just a case of figuring out what it is.