Order of photos in albums when synced to iCloud

At the moment, my partner's iPad (which is running IOS 17.4.1) stores all her photos locally. There are numerous albums, each of which contains many, many photos. She's manually sorted the order of the photos in each album - the sort option is always set to "custom order".

The iPad is running low on storage, so I'd like to sync the photos to iCloud and use the "optimise iPad storage" to free-up some space.

Before doing this, I'd like to be absolutely sure that the custom sort order will be retained through the sync process. I don't want risk losing the carefully sorted order of the photos because the sync process somehow mucks it all up.