This is just terrible.
However, while it does add a layer of annoyance that'll mess things up for most, like any DRM, it fundamentally is unsound and will get cracked. Us good people have a big incentive to do so here. Reading the spec, it still relies on a trusted party (expected to be the OS) and, unlike ie. games consoles, we already have admin access to that party from the get go.
Where it could be a problem is mobile phones. They could target browsers that support ad blocking and you'd probably need to root the phone to get past that.