Thanks again. I do agree with you in that the dealership will just say it is ok/normal.
Here is my opinion and really just an opinion. I think the change from Green CVTF to Blue is just the 2020 CVT using Low Viscosity fluid for improved fuel efficiency. This is stated in the manual I received when I purchased the car (2020 Legacy New Car Information (Subaru Corporation U2570BE)(pdf file)). Elsewhere in that document in the discussion on differentials it states QUOTE "Using low viscosity oil reduces power loss, improving fuel efficiency. Using medium viscosity oil ensures reliability." This is regards to using the low viscosity gear oil Extra MT 75W-80 verse GL-5 75-90 gear oil. In our owner's manual and in the Legacy Service manual, we can use GL-5 75W-90 as an equivalent to the Extra MT with the note "Can be used, but there is a possibility of fuel economy deterioration."
So do you want "improved fuel efficiency" or "greater reliability" ? In the Subaru TSB 01-167-08R, Recommended Materials, the Subaru CVTFIII (blue) is recommended for the 2020 Legacy/Outback TR580 it also states the CVTFII (green) can be used in the TR580 NA models like the Forester. If the two CVTFs are compatible, there is no issue. The only issue then is fuel efficiency verse reliability. IMO.