In that case, Safari should make it clear that its users should not expect web application to work well. OP proposes helping Safari do that by displaying informational banners when appropriate.
Applications work just fine. Developers have to be a bit more precise.
For features not supported, really a non issue, considering the Android update and support cycles
That's not true, there are numerous bugs especially on ios. What all browser vendors have figured out is that browser updates should be decoupled form OS updates and this is what Google and Microsoft are getting right,frequent updates, new browser engine features and fixes are available almost immediately.
A lot "features not supported" by Safari is supported by Android > 4.4.4. I can target >90% of users on older Androids and still have compatibility issues with Safari users. Unacceptable.
