I don't know but we have the same problem. Dd, 4 in July, school in Sep. I'[m worried about school as the problems start after lunch generally with soiling due to constipation. She's on movicol but it's becoming less effective. We've got suppositories - did one but it won't be so easy to do the next one
She is also resistant to doing anything she doesn't want to do no matter waht the consequences. She's not naughty - but immensely stubborn. She sat on the potty for hours today - no poo. So you are ahead of us there! I put a nappy on in the late afternoon in desperation (we usually have one toward bedtime) and imediately there is a modest poo.
We've been PT since last summer. I dread school. I don't want her to soil and be smelly. I'm also at a loss what to do about it.