Yes exactly ^ Its there for a reason. Just removing it for convenience is not sensible.
Audi exhaust pipework is metric, which befuddles most exhaust shops in the UK since our standard pipework is imperial. For some unfathomable reason, they then defer to the next size
down and hack it to fit
. Why they don't go up is beyond me. 2 1/4" pipe is 57mm so fits inside the D2 S8's 60mm pipework, but 2 1/2" is 63mm so slips over the top of it nicely and doesn't cause a restriction.
Etka shows that on the D3 the connection after the cats is 60mm so I would expect the flexis in front of it are also 60mm, meaning a 63mm flexi should work just fine and not cause any restrictions.
Curiously enough, the D2 PF 4.2 5-speed and FL S8 actually do have completely solid exhaust systems with no flexis in them, but all the other FL models and the PF 4-speed do have flexis. The S8 has stiffer engine mounts though so obviously the Audi engineers decided that flexis weren't needed in that application but were in the others.