How is the Apple Watch ECG disabled in certain countries? In Japan there will not be ECG for potentially many years until it makes it through mountains of bureaucracy.  

I haven't tried a different Apple ID to enable the ECG, but I heard others have tried without any luck. 

I heard the block is serial number geo-fenced.  It's obviously not a different WatchOS version. What happens if I factory restore in an approved country? 

When Japan or other countries approve ECG existing watches will suddenly have ECG so how will it be enabled? 

Do you think this is simply a matter of setting the region, pairing a blocked Japanese watch to an American iPhone and using an American Apple ID?
According to a few 2018 articles, the restrictions are based on the region where the watch was sold, and the removal of blocks is implemented by a watchOS update. 

Not tied to ID. No geo-fence. 

There was speculation that changing the watch's region settings could bypass the restriction, but those articles correct that understanding. 

Given these facts, the easiest way, and the way that fits the common programming design patterns, to restrict by region would be to disable globally, and with an OS update, enable the feature for the regionally purchased devices, likely by serial number/factory code.


As for which watchOS features are enabled for which country, Apple provides this handy list. The UK is listed as an approved country for ECG since watchOS 5.2 (March 27, 2019).