The 375s never run the Sheerness branch, although a 466 shouldn't be out of the question. However, the likelihood of seeing this is low as its short and they're unlikely to remake part of the current Southeastern route to accommodate this (which would be needed I think). Medway Valley Line is possible though.
I see. Must be misremembering somewhere. I was going off the 465 in game covering Sheerness services, assumed 375s never did.
466s got taken off the Sherness branch in favour of 375/3. The 466s are now adding onto 8 car 465 sets