For me, using light-themed software for a prolonged period causes my eyes to strain and my head to ache. Sure, they do so to a very little extent, but the uncomfort is often distracting if not tempting me to slack off.
So for me, yes, dark themes help me get in the zone much easier. But of course that has very little to do of the colors scheme itself.
I also get a somewhat soothing and focusing effect when using a dark theme, especially in a room with dim lights.
But what absolutely destroys the experience for me is when I have to look something up on the internet and end up on a page that doesn't honor the browser's dark mode. The switch between bright and dark is extremely jarring.
Biologically, no. Pupils constrict when there's more light, which makes the image hitting your retina more focused. Sharper images can be resolved faster, when means your eye can relax more. For some people this can reduce eyestrain.
However, some people are sensitive to light, so the optics are not the only consideration.
I've seen research that supported that idea and research that didn't so I'm not sure it is possible to provide a definitive answer to that question.
As a colorscheme author, though, I can attest that working on a dark background gives me a lot more "range", so to speak, than on a light background, which tends to make "dark" colorschemes much easier to create and more expressive.
For me, the sweat spot is at around 10-20% lightness.
For me, using light-themed software for a prolonged period causes my eyes to strain and my head to ache. Sure, they do so to a very little extent, but the uncomfort is often distracting if not tempting me to slack off.
So for me, yes, dark themes help me get in the zone much easier. But of course that has very little to do of the colors scheme itself.