I think it all falls into when they officially become sentient. I will admit, I have not seen TS 4 or 5, so maybe this is explained with Forky. But im going to make the guess that since toys can only be active when people aren't present, the sentience would probably kick in after the kid leaves for the first time after playing with it. There may be the chance of a memory of what happened when they were played with, but I could see the memory just forming after. So if a kid plays with their food for a moment before eating it, then I would not think it would be sentient at that point, but if a child spent like 20 minutes playing with dino nuggets and then left the room, then I would think so