Sure, it makes sense that animals would not eat poisonous plants. I’ve noticed my dog occasionally chews on certain plants, while pointedly ignoring the surrounding grasses.
As a prepper & forager, I’ve tried the plants my dog likes, and found them delicious, often having medicinal value.
The rule being, approach with caution, in small quantities.
I don't know if it would make sense or not, but even if the animal ate something and got sick (when our cats would have a bellyache, they'd eat grass, which made them throw up and feel better) and/or died, the human observer would learn something from that too. There are some plants that are tricky -- parts are poisonous, parts are good; some are only bad at certain times of the year.