It's most certainly not scientific writing. But I think that is not the point of these publications -- they are meant for a wide audience.

So I think I should interpret your criticism as saying that quanta does a poor job in maintaining rigor while trying to explain advanced topics in mathematics and theoretical physics to a wide audience. My impression, on the other hand, is that their reporting on these topics beats similar publications hands down. I am therefore happy to recommend it to interested laypeople, for example to my (few...) friends outside of academia and to people here on HN.

By the way, I hope you realize that these two viewpoints are not completely orthogonal.