[derefr]

But it being an unsupported method will hopefully at least cause the middlebox to generate a 405 error, rather than undefined behavior.

[water9]

Rather than a 400 error?

[derefr]

No, rather than the body being silently ignored in the caching (or even proxying!) logic of some middleboxes, because "since GET will never have a body, for efficiency, we won't bother to check for one."