TLDR - The selection styling has minimal contrast between the background color and text color.
The hover background is hardcoded so it is not affected by theme at all.
In that context everything is “hardcoded”/defined.
Regardless, it is something that should be considered from a UI/UX view. Therefore, the selection colors should be altered accordingly/added to the selected theme.
Even things like grey/blue/red/[what ever basic color] get a css variable so it can be properly themed during add a new theme.
But the selection color somehow didn’t got one.
So I think that looks more like a mistake instead of something done intentionally.
And because it isn’t affect by a variable. No one will ever realize there is something need to be changed there.