I noticed what I call "hood flutter" on my 2019 fairly early on. As time went on, it got worse. I eventually stumbled across the TSB, and by the time I asked about getting it fixed, I was told it is a cosmetic issue, I was about 3k beyond the std warranty, and even though we have a Gold extended warranty it's not a covered repair and would be about $425 to fix. I declined and wrote directly to Subaru because, at least to me, it truly felt like a safety issue - I fully expected metal fatigue to eventually allow the top of the hood to peel off and flip up over the car, if not worse.
Subaru corporate issued me a coupon to cover most of the cost, and when I did have it fixed, the actual cost was much less, around $200 if I remember.
That was last summer, and it did help. But in the last month we've had some fairly windy days (30+ mph) and it looks to me like the flutter may be coming back. It doesn't sound like an overly difficult repair, so once we get warmer weather, I may take a look and see if the bonds have broken again. As a Robert M. mentioned, this requires removing the insulation under the hood, and from what I can tell, the clips that hold it on aren't reusable (dealer charged for them, both when they originally confirmed the problem and again when they made the repair). If I end up needing to repair it again myself I'll probably look for a better bonding agent, as the specified 3M part doesn't appear to be up to the task. I've never had a hood that moves around like this one, and although my F150 has an aluminum hood, it's rock solid under every condition so far. I also still have to wonder about eventual metal fatigue, although Mr. Mauro's 98k experience is comforting. It does make me wonder if there is something different about newer models in that they don't seem to exhibit this problem...