I am not entirely sure you did anything wrong. Have you emailed the developer about this? There may be a bug in syncing data between devices.
So I contacted the developer... he said 'it takes a few days' bahh... Could sync isn't supposed to 'take a few days..'
So I messed around with it and found a fix... I set high score and did some unlocks on my phone. Tablet didn't sync 'for a few days' -- figured out that if I sign out of Google Games on the tablet (Settings > 'Sign into Google'), close the app, reopen the app and sign back in to Google Games -- it insta syncs. BAM -- problem solved (sorta)
NOTE: On Temple Run 2, coins and gems are device specific, so that never syncs. What does sync are the stats and unlocks. So if you unlock an upgrade, that WILL SYNC...
You just have to be cognizant of which device has the higher score, and only unlock stuff on that device until you sync it. Yeah, it's kind of a PITA, but at least it works.