I.. agree. Them having those policies is what makes this presumably a business and not a standard. Maybe something like this is better implemented closer to how BrowserID is (or am I talking out of my rear?).
I can assure you I am not thinking of using the homescreen in that way, since I never experienced android when it worked that way.
In the context of checking inboxes, adding an "inbox" activity does make sense, especially if you receive multiple notifications. Although I don't see why there couldn't be a way for the inbox activity to only be added when necessary.
This gets to be particularly annoying if you, for instance, check multiple folders.
Of course you can just hold back to quit the app, but that would be an obvious solution, and put designers like this guy out of a job.
As for "no satisfactory solution".. the first thing that comes to mind is having the notification take you to the inbox, but then open the message itself, thereby building the "stack" properly.
Other than that, I'm intrigued.