People identified and named in Lightroom Classic should fully sync to Lightroom Cloud.
I have a Lightroom Classic catalog with 30K photos and named many people using face detection. I've also made sure my keywords list is flat (no folders). I recently uploaded my photos to Lightroom Cloud so they're now synced. Unfortunately, none of the people show in its People tab. However, some photos do have a keyword of the person's name. So now it seems I have to re-identify all those people again in Lightroom Cloud. It'd save me a lot of time if it named people synced to the cloud.
I'm not sure what the future is for Lightroom Classic, but if it's going to be sunsetted with no planned migration, I rather know sooner rather than later to inform how I should best invest my time.