It's not even about sleep anymore. That was what f.lux's intent was back when the research first came out, but now it's been morphed by people trying to sell these glasses into "blue light is harmful". They talk about it like your eyes are getting damaged by blue light. Or that it's defending against eye strain caused by blue light rather than just overall luminance.

> They talk about it like your eyes are getting damaged by blue light.

I think this is somewhat reasonable, since the issue is that the UV comes from, specifically, shitty light sources that are attempting to make blue bits of the spectrum (led and fluorescent).

https://pmc.ncbi.nlm.nih.gov/articles/PMC3222423/

All of this is debunked in the documentary above.