The dealer won't do anything. They'll brush it off as not a big deal and tell you just change the oil more frequently and have them do it since they use the "good" oil.
He needs to call all the local news outlets to get a story pumping. If it was me I'd be screaming at the dealer so loud they would fix it just to shut me up.
Studied exercise physiology in college - most people have no clue how significant ergonomics are on everything in life. It's like a placebo effect on steroids
You all are looking past a super simple solution.
Take the Motorcraft oil, store it somewhere cool and dry.
Run Dexos oil thru the warranty period. Switch to Motorcraft when warranty is up.
Really we need to stop making things hard on ourselves. This is trivial.
Personally I'd use an HDEO 10w-30 conventional. There's a guy on YouTube, Mr. Subaru, who owns one of these. He has plenty of videos on maintaining it. If you ask him he'll probably answer on his oil choice.
Whatever the door jam sticker says for tire pressure, go 5 psi over that. No, you will not hurt the tires. The day I got my Subaru I inflated the tires to 40 psi (door sticker says 32) and at 60k miles the tires still had even wear.