... just that you keep overlooking the .041% part, which is obviously a trace gas by percentage ...
So?
If I put one drop of black ink in a glass of water, that will represent about .041% of the solution, yet the solution will become opaque.
And so crumbles your "But a trace of something can't absorb light significantly!" argument.
A tiny sprinkle of cyanide in a glass of water would be similarly dilute. By your standard, you should have no problem drinking it. It's just a trace, so it can't be harmful!