I think you might have mistaken about the capping system.
There’s a specific all zones bus and tram capping (as you said at £4.95) because all buses and trams in London are of one fare hence counted as one zone with no zonal distinction, and there are zonal capping that includes underground and trains, just like the Travelcard preceding Oyster and contactless ticketing.
So, if you take buses anywhere but just the underground in zone 1 and 2, you’d be capped at £7.70, the fact that you take the bus outside zone 1 and 2 notwithstanding.