In my headcanon yukkuri filling has something 'different' about it, that only yukkuri can notice. Poo-poo is stinky and uneasy whether the yukkuri knows where it came from or not. My inspiration was the Patchouli that died in Mother and Daughter by hy835230 - specifically post #47773.
So, in my yu-niverse, this would be a very boring experiment. =)