Yea, but his point was that GET requests should be idempotent.. when that's not the important part of GET. That's why I used the example of GET /door/open, because that is idempotent, but it's still gross - it's causing a state change from a GET request while still being idempotent.

GET being idempotent is not the issue the author was dealing with. State change from a GET is the real issue.