Someone very close to me suffers from ARFID. Imagine if you will that you were in the situations above. How long would it be before you tried eating dog poop? If people were telling you dog poop was safe and healthy and the only way to survive yet for your entire life you've known otherwise.

This isn't the greatest example, but that roughly gives you an idea of what someone with ARFID might be struggling with in those moments and why it is different than just picky eating.

In the more extreme cases, I'd assume never, as it is with Bulima and Anorexia, though I can't find anything online that specifically mentions ARFID.

Remember that guy who took a bunch of babies and had them raised without any affection and minimal contact to see what the original human language was? Maybe we can get him to do it

I know in my case I’ll go 4-5 days without eating something if I can’t find anything that won’t be awful.

A friend of a friend got into coma once because of that, their parents apparently didn't thought that it's psychotic to starve their children to death as an experiment and a teaching moment

Dread by Clive Barker (Books of Blood Vol 2) explores this, if you want a fictional answer.