I'm gonna lean in to your side. I've noticed ever since switching to a dark theme in my code editor that at the end of the day my eyes feel less tired. BUT (and big one) on the glossy screen of my phone, dark mode feels more straining to the eyes... How can this be so?
My notebook has a matte screen and barely reflects ambient light(s) back at me. I say barely to avoid saying "none" because surely someone will nitpick that it is reflecting a small amount of light etc.
The phone has a glossy screen, and it reflects every single thing it can back my eyes. Dark mode makes it even more "mirror like". And while I prefer the colours (specially if you're using the phone at night, with no ambient lights to bother), I acknowledge that it is more straining during most of the day. Even at night when it autoswitches to dark mode, I'll have some ambient illumination unless I'm at the cinema (not for a couple of months since lockdown) or basically trying to sleep (and I know I shouldn't be checking the phone if I'm trying to sleep).
Another data point: reading PDFs of books and conference papers on my computer (black on white) is tiresome, whereas reading the same on a kindle feels amazing. But then again, the kindles have won this battle a long time ago and nobody should be trying to read books or other media made for plant-based-paper on a screen anyway (and here I give e-ink a bit of leeway and consider it more plant-paper-like than a screen).