One would think the sound insulation would dampen that. I don't hear my cable rattle around in the e-tron. Looking at the photo above, the cable should fit beneath the floor with no problem. That area at the rear of the vehicle is where the subwoofer is located, beneath that plastic cover. Maybe someone that has received their vehicle can speak to this on the EV6. I'm not sure about the UK cable and how long they provide but I have seen some videos with them being long, in some vehicles. With the number of DC fast chargers you guys have in the UK, do you travel with them all the time? I'll admit I drove around with mine in the early days of getting the e-tron before figuring out how things really worked with charging. Now it stays in the garage unless I am taking a long distance trip, where I want to have that security in case there are issues with DC fast chargers. One thing I have heard folks recommend is to buy a 50 ft, heavy duty extension cable when going to visit families and need to plug in at their house or camp sites that has NEMA 14-50 plugs available.
I think the false floor would be fine for the cables we get in the US