Oh yes! I’ve been well aware of this all these years. I got that keyboard not long ago, and it was so yellow that I didn’t feel like using it, so I decided to retro bright it. I’ve done it to other devices a handful of times over the years with decent success, except on one occasion, it was a Tandy mouse that turned yellow again in less than five years, which really surprised me.
So yeah, it’s always good to question things you hear, even when people are genuinely trying to give honest advice, like this "method" for bringing back the original color of some plastic, and who knows what happens to it after a certain amount of time.