The “hidden” manual you speak of sounds like the updated info from Hyundai
Yes I received a new stick label from the dealer, I asked them to post it, as I couldn’t be bothered to do a detour just for that, However I have missplaced it, so will ask for another when it goes for a service in March. The only thing different from the original below that was more akin to a DPF – was the inclusion of repeated “deacceleration” which will cause the engine to run lean and increase the oxygen increasing temperatures in the GPF as you have said.
Hyundai are aware of the problem and is working on a fix (software update) and I expext Kia is doing the same. Hyundai has said it will take time and don’t know when a update will be released. There are no official recalls with the Sportage or Tuscon showing. One thing I will mention is the label with the new instructions on had my dealers deatails on it, and didn’t look like it was from the manufacturer. That said is the rcall you mention just another dealer issuing updated instructions!
My original manual showing similar instructions for a DPF
