Yet, given enough demand, and a explicit recommending nod from the spec, these will comply. It's not really as big as problem as everyone seems to think. And it's literally the same amount of work of adding a new verb.
[1]: https://bugs.chromium.org/p/chromium/issues/detail?id=14801 [2]: https://bugs.chromium.org/p/chromium/issues/detail?id=452335...
So while I agree that it would be nice if everyone respected a "living standard", my hopes for middleboxes to comply are not high.