Isn't this well known? The human retina has fewer blue-sensitive cone cells, and very few in the fovea, which sees the sharpest details: https://en.wikipedia.org/wiki/Cone_cell#Distribution

From the paper's abstract (emphasis mine): "Wavelength influences multiple aspects of visual performance, yet its role in spatial resolution remains incompletely understood due to confounding factors such as luminance differences, chromatic aberration, and intraocular scatter."

They then did some modeling to estimate how well the results could be explained by scattering, chromatic aberration and, neural sampling (the cone cell density factor that you mentioned). They concluded that none of them could completely explain the observed results, but their results seemed to suggest the bulk of the effect is due to optical effects, with neurological factors as a secondary cause.

Refining existing knowledge by examining phenomena in more detail is how science should be done. The pressure to focus on discovering entirely new things is a major cause of the replication crisis.

Here's a neat demonstration of this https://www.schulz-hildebrandt.com/9-purple-dots-illusion/ (I find the effect works much better on my phone screen than desktop)

Well, the title here at HN implies something else than the study shows.

If blue light actually impaired vision, that would be very notable. It would mean that removing the blue 'channel' for an RGB image would improve acuity. This is not what the study showed, however.

It is mainly just the basic fewer cones bit you mentioned. Which, btw, is easily experienced if you ever look from a distance at neon or led signs that only emit blue light. They'll persistently look out of focus when compared to their surroundings.

Yeah. I worked in the optical industry to pay for college. That was decades ago and one of the Drs I worked with and I had discussions on this. It was interesting at the time as I knew very little about optics when I started.

Blue Blocker glasses were a thing since the 80s

I certainly thought so. I have astigmatism and I cannot for the life of me read blue LED/neon signs at any reasonable distance at night. Any other colour, no problem. Blue is just a blurry mess.

I get that the guy needed to write a paper on something to get his PhD (in psychology, which might explain some of this as well, I thought standards were a little higher in the hard sciences), but don't know why it deserves a high profile. At least, based on merit.