I suspect that the Audi dealer service departments in smaller markets have less experience with R8 oil changes (speculation on my part).
If you have to remove a small amount of oil, how would you recommend to do it?I don't believe the sensors are finicky per se; the engine is just sensitive to overfilling - from memory the volume between top and bottom of the scale is less than a quart. If they can remove some oil easily it should not take them too long to get it right; I'd be interested to know from where they drain it if you can ask them when you collect. Yes you have to let the engine run for a while or take a drive before you can see the oil level reading. Hopefully you'll be back on the road in no time.
Going forward always measure the oil out on an oil drain. I fill up with 7 litres which results in the message to add more oil car driveable, then add in 200-300ml increments, driving a short distance to see the oil level meter. The oil change volume should be 8.3L and on the two occasions I changed it was spot on. Never add a full litre / quart in one go if the oil is at the lower end of the range.