Why has the display control panel pointer truncation bug gone unfixed for long?
devblogs.microsoft.com
devblogs.microsoft.com
Microsoft does not care or extremely sucks at quality assurance.
By the way, if the app wouldn't respond in time, what should happen with the icon? What would happen if Explorer removes the icon but the app which still thinks it has - would update it?
What happens if your NotificationAreaAPIv2 is not widely adopted?
What happens with the apps what were never adopted to your v2 API? (You still have the problem anyway).
EDIT: And what happens with the old apps when you deprecate the old API?
It's maybe a bad API design, but in the end every app developer can fix it for their apps.