I have done a drain and fill every 1.5 years aprox.. I always use sp-III because its still under warranty.. and hyundai well is known for being terrible about warrantying transmissions with aftermarket fluids.
First off Hyundai WANTS you to use SP-lV-M because it is a better ATF that superseded the sp-3
By USA law Hyundai can't deny warranty as long as the fluid you put in has been speced by the oil manufacture to be compatible with their oil spec.
I had a Fram Ultra on a Hyundai Elantra that had the Hyundai Tick of Death at 14,000 miles and they questioned that they had to test it with theirs and they don't advise me to use the Fram Ultra. I said the Magnusen-Moss Warranty Act states I have the legal right to run that filter. They did not say a word after that. It received a new long block after approval. And believe me, they stated to corporate I had an Ultra on it. Hyundai is terrible about warranting anything that cost them money. You ALWAYS have to be ready for a fight with Hyundai if it is big ticket.
I have relitives at both the largest Minnesota Audi and Lexus dealerships, both say they never check oil for warranty. All they do is check if it is full, check if it is AFT or gear oil in the engine oil and if all is well they warranty it. Both have worked there 10 plus years. Not a single sending of an oil analysis. Too many forum dogma warranty and go by the manual types drum up fake news on how dealership work with warranty issues. We hear techs from all different states and makes say the same thing. As long as it is not ATF or gear oil in the engine oil and it is not more then 1Qt down, you get the warranty.