Interesting. I wonder if this technique could be used as an olive oil purity/quality test of sorts? Maybe correlating a few samples of various kinds, along with some external form of verifiable testing, it may be possible to figure it out.
The article mentions differences between brands, but IDK if there's a specific correlation with quality other than that fake olive oils certainly won't turn red/pink.
I always assumed that products like olive oil sold in thick green bottles were sensitive to degradation by (UV, sun)light, so if that is true then by definition a casual in store test is not going to work. But perhaps green bottles mean nothing vis a vis light.
I do recall that brown bottles were a thing in brewing to prevent beer from becoming funky by the action of light, but perhaps oils aren't susceptible to that.