I received my device on monday after it was nearly two weeks in service, cause of the yellow tint issue. They changed the handset. Before i had 12W10 AAAB.
Now I've 12W08 AA CB5 and of course also a new IMEI. Both were on Touch Firmware 7.
Tested it yesterday extensively and reached a temperature about 48°C with a little help from the sun when the XS was in the car.
There is NO yellow tint on the bottom and on the edges(left, right) of the screen anymore when i checked it via the white service screen (*#*#7378423#*#*).
But there are very, very, very, very light tints at the top in the corners, left and right, when the device is upper 42°C. They are really very, very hard to see. I discussed with my gf about them. She didn't see them. If i switched from white to the black, red, green screen they weren't visible anymore! On my opinion this issue is fixed for me, if the tints aren't getting stronger and new tints appear.
Will check it the next weeks and keep you informed, if it gets worse!