This appears to be the paper: https://hal.science/hal-05385645v1/file/Monico%202025.pdf

[edit]: this is clearly not the paper, as it was published in 2025, and the hn link is from 2013. Regardless, it makes only passing mention of commercial LED, certainly nothing that supports the claims in the article, nor does it mention in the paper body anything that appears to be referencing previous analysis of the lighting, so the search continues.