They need it for remote hold. It's more important than you may think. And Bravo extension doesn't make much difference when runway 26 is in operation, so it's better to park them over there. By the way, the plan was to put next one in run up bay but luckily Gatwick reopened.
there were two in the run up bay overnight early on Friday morning... the ivalo and agadir diverts were towed there after offloading passengers on the taxiway.