And it didn't exactly offer it, as in "why don't you try this?" The AI was set up so you could give it some ingredients and it would make up recipes that used those ingredients.
New Zealand political commentator Liam Hehir wrote on Twitter that he asked the Pak‘nSave bot to create a recipe that only included water, ammonia and bleach
When you mix ammonia and bleach you get chloramine, the AI was basically told to make a recipe that would produce that.