Each yearly iteration of Amazfit products ship with a different OS version, generating a huge fragmentation of the platform, making it impossible to support all the devices at once while being able to use the latest features.
Here's every amazfit device and it's OS version
On the first watch I developed the app for, an Amazfit Band 7, I noticed that the device became hugely unresponsive to the point of sometimes not turning the screen on at all, I believe these might have been caused by a memory leak in one of the previous versions of the app, that never got away.
Factory resetting the device didn't fix the issue, and when I asked for help on the official channel I was told How much you pay for is what you get and nothing else.
I believe that while the platform can be a good starting point for people to get into development, it's not a good idea to develop a full fledged app for it, as it's not a stable platform and the manufacturer doesn't support (you) the developer. Open sourcing the operating system would be a good idea, but I don't think it will ever happen.