childPosition not a valid sort option for /wiki/api/v2/pages/${contentId}/children?

Calling REST to get child page with an explicit instruction to sort by child order returns a 400

const response = await api.asUser().requestConfluence(route`/wiki/api/v2/pages/${contentId}/children?limit=100&sort=childPosition`);  

Does anyone else experience this? The docs don’t indicate that there are limits on which fields can be sorted.

It’s not a big deal because the natural order of the results is this order, but the behavior still seems odd.