There are times when we get a stark "no" on the potty- but it's just that my baby doesn't have to go, so I wouldn't call it a "strike". I'll try to encourage my baby to stay on the potty for a little while just to make sure, but my baby's figured out "potty=pee" and if it's not time to pee, then it's not time to be on the potty. It's possible that when you sense a "no" this is what's going on, you've just misguessed (unless she goes as soon as she gets off, of course). Just today, I got a "no" 10 minutes before my baby actually had to use the potty- bit frustrating, but it can happen.
It sounds like there may just be times when your baby is uncomfortable, if this mostly happens after you eat something weird. The shifting may try to be getting into a more comfortable position, or trying to figure out the right position to get it out.
I agree that "strikes" are an adult concept. It's not uncommon for a strike to coincide with a milestone or sickness or something similar, so the baby is just redirecting energy away from potty awareness to what's more important. Sometimes "strikes" are babies learning their limits, they try to hold it in as long as they can and can only learn how long that is when they can't hold it anymore, which doesn't usually happen on the potty.
I recently got over a cold and because of our experience with EC, I was hyper-aware of the level of awareness of my body that's required to know when I can hold it 10 more minutes and when I need to rush to the bathroom as well as the muscle control required to be able to hold it. It takes time to learn that, and our babies are working on that.