That seal must be quite a challenge to replace unless they somehow can get the oil pan off without removing the engine, and if its not too hard to remove everything below below the engine to access the oil pan, like the whole sub-frame that must hold the front suspension and transmission to the car.
I must say that this is the first vehicle I've owned that I have never climbed under, so I can't render an opinion. This is also the only vehicle for which I've bought an extended warranty, and a routine maintenance service agreement. I usually do all my own maintenance and major and minor repairs for that matter. Call this a hidden cost of ownership for these highly complex motive systems.
Anyway, either they didn't bother to replace the seal and put in some "Bars Leak" with great hope, but the leak started up again, or they botched the job and the new seal didn't take, or, the crankshaft has issues with that seal's surface and the engine needs to come apart. So, hope that the new seal didn't take for some reason and that they can get it right this time.... I'm sure they've never done a rear main seal replacement on an eTRON before, or after, yours.
1. The original main seal shouldn't leak for many years.
2. A new seal shouldn't leak for many more years.