I think he is over-stating the case but the core idea isn't wrong.
More important, though; they *will* get away with it and there is nothing <idpf> will do about it.
Not. A. Thing.
That message is now out in the wild.
ePub3 brings a lot of useful stuff (and a few nasty surprises) and is going to be the core format internal to the BPHs, but there literally is nothing to prevent retailers (or other publishers) from embracing and extending it to serve their specific agendas, especially in asia and other protectionist markets.
Let a thousand (incompatible) epubs bloom.
This is what lack of enforcement brings.