It might be less about health and more about the fact that low-quality bacon is almost all fat.

Yeah, this is really what you'd determine comparing brands. The mega brands like hormel, oscar mayer, etc will almost always have massively imbalanced fat proportions, and a lot of the time the smaller, or more expensive brands will be a lot closer to even. Fat's delicious in bacon, but it needs the muscley bits to hold it's own and not taste like chewing on lard.

I seem to recall people (felt they) couldn't identify leaner bacon or some felt they were being ripped off because not enough lean, just fat. All about the time, IIRC, that fat had began to be loudly vilified by the health community - butter, cheese, meats, milk, and as a whole believed fat unhealthy. That was likely perceived a hard sell to health-conscious customers, so they hid the fat.

And, on top of it, they don't show the back window in question.

I thought I was missing something. I'm glad it wasn't me.

I think it is fairly obviously this, quote from the article:

the consumer sees a relatively unbroken field of red protein, creating the illusion that the bacon is leaner than it is.

Fat is bad, so it's hidden. But fat tastes good, so if you look at the back window, you see it.