Bluntly, if you were using Pay as You go Oyster on that journey, of course you’d be expected to get off a train and tap in or out at the Oyster boundary. That’s the way the system works and those are the rules of accessing it.
Just because it would be inconvenient to the traveller isn’t a reason that they could skip a step. The option exists to buy a through ticket or use contactless and avoid the stop so choosing not to take those options is accepting the need to work within the rules of the oyster system.
I think that having a travelcard covering the whole journey out to the Oyster boundary as well as a paper ticket from there would be about the only way to legally do the journey without getting off a train.