Like anything else, it may be a matter of amounts & sensitivities. Lots of things meant for human use (consumption or not) contain things that in small quantities may be beneficial, but in large quantities make us sick or even kill us. Alcohol is an example; for years, experts have been telling us that for many/most people, one or two drinks a day is ok - may even have some therapeutic value for some people. A lot of drinks will make us sick, and too much alcohol will poison us and do liver damage. And there are of course some who shouldn't consume any at all.

The articles I read said as much with the Xylitol in products intended for pets - very small amounts (but that's also why I mentioned reading labels). The emphasis wasn't on those products, but on the products intended for humans, who don't have the same sensitivity to Xylitol, that are likely to contain much more.

...And when it comes to "food", dogs don't know when to slow down/quit anyway.

Doc