Although it took way too long to add support for this (three years? really?), I want to commend the team for finally delivering on it. Especially the specific capability mentioned above to reupload existing photos since presumably everyone who uses the photo sync has a backlog of older live photos that would be a herculean effort to resync without the functionality built-in. Missing this would have been very short-sighted and I was actually concerned it would be missed in the rollout.
That said, there are two significant things still missing - the ability to download the video file from the web and the ability to sync the actual live photo to my PC. It appears when syncing it is still just the still photo file. Viewing on the web is nice, but it is so slow to retrieve full resolution images it is unusable to browse through an album - much easier to do when all the data is pre-loaded on my desktop.