He addresses this point specifically in his post ... developing it as an extension would reduce the features he can support, and further entrench it in google's walled garden (since he'd have to publish it on the chrome store).

I don't have much more context in this person's project than anyone else, but your response is kind of the point, one vendor has too much power because they can't be expected to support any kind of innovative ecosystem; yeah, that's not a great state of affairs, and begins to echo/suggest anti-competitive practices (whether on purpose, or just as a function of their size)