That’s a really good visual illustration of the improved packaging at the rear.
As has been said, it may be that Renault as the engine manufacturer have been more conservative in terms of approach - Bob Bell talks about reliability as chief objective (
https://www.motorsport.com/all/photo/ma ... 07027&s=-6) - and that may be based around the limitations of their engine. Perhaps RB prefer to ensure they’re creating optimal chassis to continue to improve understanding from an aero side, with a conscious sacrifice of reliability, given that they know they’re likely to be using a different engine next year anyway? A bit like how McLaren wouldn’t sacrifice their downforce levels in the Honda.
That said, I do think there’s more to come in the bargeboard area, so they’re probably trying to keep solutions there under wraps until testing.