API call to set manual product sort order within a collection?

There seems to be two API endpoints that are made to reorder collections.

REST Api - Updates the ordering type of products in a smart collection

and

GraphQL - collectionReorderProducts

The REST endpoint seems to be broken when it comes to reordering products - don’t waste your time with it. Ask it to move 20 products to the top of the collection, and you’re lucky if it moves anything.

I’m testing the GraphQL endpoint now - hopefully it will work.

Something has to work, because the app ‘Power Tools Suite’ is able to shuffle collections randomly, and I think the above endpoints are the only ways that they could achieve this.