Here's my theory: there's two type of blond hair: super dense, ala Brad Pitt, where hair can even be spiky and has the texture of dark hair but with a different color, and super fine, a la Bieber, where the hair creates those wavy patterns like in the photo below. I believe we're both in this last category.
I think it's normal to an extent to have that appearance in the sun. I think I've got a test for you, this seemed to work for me: comb your hair over (kinda like how pewdiepie does it), such that you have hair covering all of your head. If you still see through to the scalp, then it might mean that you have a problem with your hair, otherwise it's normal to get worse hair under direct sunlight. If you're lucky your frontal hairline will also not be see-through, I finally can't see through my hairline for about two years now after taking some vitamin supplements (unrelated to my current recession tho), but as you can see in the Bieber photo that can happen too and sometimes it still happens to me if I go for a bolder hairstyle.
I believe this is accurate because the hair everywhere except my temples is super thick, even more so than my back and side hair, and you can still see the scalp with a shorter haircut / if my hair is standing up like Linus' haircut.
It's just a package deal with being blonds, and we have to deal with it. And even Bieber in his older photos has a thinness that can be seen "under" the haircut, in this photo (circled with red):
So basically, our hair excludes more crazy hairstyles because it's just gonna look thin af even with no dht