there's tons of "studies" and shit that do reccomend some products over others, but usually are just a pile of shit funded by companies to give you reasons to buy their products or not to buy a competitor product.

just because there's a "study" or claims it to be science or uses some fancy words, doesn't mean that they can actually be trusted, especially if you don't know what are you talking about.

anyway, about other stuff that's not supposed to be feed to dogs because it causes them isssues, but they still feed on them, it might be because of ignorance, they might assume that since they eat that stuff, also their dog can eat it not realizing that they are a different system.

I would stop thinking about it, probably right now there's a dude feeding some weird stuff to his dog, and you can do nothing about it