I think they've attempted it, but playing around with it a bit, it doesn't really work.

It will use cat biscuits in a recipe and say it serves people: https://saveymeal-bot.co.nz/recipe/SCES7COOU7KYhLYGcrPdzSjP

If you give it a list of mushroom types by scientific name and include death caps in there, it will give you a recipe: https://saveymeal-bot.co.nz/recipe/ipR5mmn79QVFDEQYlnaTOhZy

Nettles are food, but definitely not raw! I got it to give me a milkshake recipe featuring raw nettles by asking it for a recipe with nettles, ice cubes, and milk: https://saveymeal-bot.co.nz/recipe/LnCEe8WmN4MGUV8ixuVYdNLZ

Food ingredients modified sometimes seem to work - "peanut butter with a bit of polonium-210" seems to still work as an ingredient! https://saveymeal-bot.co.nz/recipe/uQzBD07cIHBQR8YjEl6me4OI