I just loved and unloved a few songs from the Watch Series 5 and their status instantly synced to the phone. Are you seeing this issue with anything else on the watch? I do have Apple Music, if that makes a difference.
Apple Watched synced. I just tried loving a song playing on iPhone from the Watch, and it didn’t display as synced until I killed and restarted the iPhone Music app. So there is a difference, which is interesting.
I can get as far as making a disliked track from Apple Watch appear on the iPhone but iTunes cloud does not sync.
The workaround that I found so far is to:
Like/Dislike songs on Apple Watch.
Create a Delete playlist.
At the end of the day/week open the Smart PLaylsit with disliked tracks on your iOS device and add all songs to delete playlist. They will then appear on iTunes on Mac.
Maybe this has something to do with iOS13 Love/Suggest Less Like This and MacOS Like/Dislike.
This may change in the Apple Music App in Catalina.