I think that’s your opinion, I am not sure I agree doing both is all that “odd”, though I really don’t care much either way. Notifications are very important though, certainly enough to justify an icon and a textual treatment at the same time.
I just feel like this will be a user pref used by a tiny, tiny percent of people. There is a reason this is in “GMail Google labs” and not part of GMail proper. I don’t want to clutter user prefs with a bunch of super rare stuff, so would rather just have both modes active all the time.
I also think this point is important.