I’ve seen the videos, read the analysis, and after years of debate still remain unsure of the “best tires on the rear” theory. Wes, 2-cents, and OK4450 have described my reasons perfectly. And I believe it’ll vary depending on the vehicle. On pickup trucks, the rear ends (on some) are very light, the weight distribution highly rear-biased, and the rear end occasionally has to carry loads, so it would seem ridiculous to me to NOT put the good tires on eth rear, yet on Corollas and such the thinking of the three aforementioned posters reflects my own exactly.
Personally, on my car, I prefer the good tires on the front. In this litigious society, I can understand why many shop policies require the better tires on the rear. I could elaborate on what I think of the tort law system, but that’d be straying too far from the subject.
I think tire rotation is oversold. It does allow tires to wear out in sets of four, but it can also mask irregular wear causes. However, the OP has a Subie, and on those cars rotating makes more sense because of their design weakness (my opinion only) of Xfer cases prone to failure from what should be considered a condition within the normal scope of how a car is used.
To the OP I say you have no problem, I commend you on your attention to your vehicle, and you can sleep soundly.
A tire tread depth gage is dirt-cheap, and it’s worth the few bucks to help you feel better. You may want to spring for one. I have a friend who just had two new tires put on a Corolla, and the tire gage was worth every penny just to be able to show her that all the fears that some of her well-meaning family members had scared her with were bogus. The difference between the new tires and the other two (just installed last fall) was within the interpolation range of the gage, within normal variation of any tread.