As a few others have mentioned, Toyota now sells the Tokyo Roki Subaru Filter and honestly this is a huge +1 and win in terms of convenience and also for those of you who take your car in for scheduled services instead of DIY. For the outgoing model, Toyota sold their own oil filter and I can't really comment on the quality of them, I never ran them on my 13 or 18.
The tokyo roki is quite in fact the BEST filter you can run on these cars. They are competitively priced with other "premium" filters and before you used to have to go to Subaru or Amazon to buy them.
It's a bit confusing, but don't forget that your GR is a Subaru at the end of the day. Most if not any OEM part you buy for this car with a few exclusions are going to be stamped by Subaru. The same way if you were going to buy a Jaguar F-Type, you would see a lot of OEM parts stamped by Ford as it is a Mustang S550 Chassis.
This is pretty common across the auto industry.