On a tangent ... I don't own a 1DX and probably never will, so I never looked at the specifications. This thread actually made me do just that by pointing out that the operating temperature of this "professional-grade" camera is (only) zero to forty degrees Celsius with less that 85% humidity. In my (not so) humble opinion, that's pretty pathetic for the "top-of-the-range", "professional-grade" camera from a company with the (perceived) reputation of Canon!
On topic ... I sold my EF 40mm f/2.8 STM lens because it backfocused. This was apparently within specifications and I was told to upgrade my cameras to AFMA-enabled models to solve the problem.
I live in Florida and it's a rare shoot where the humidity is less than 95%, especially at dawn. You get used to it, sort of. Anyways, from the 450D to the 1D X, 18-55 IS to 300 2.8 II IS, I've never had an issue. I've shot with Canon gear in 105F temperatures with 85-90% humidity as well and have never had a single issue. I have never noticed the specs before this week and don't care about them because they are the "Working Temperature/Humidity Range" as in the safe range. Canon doesn't specify the minimum or maximum range (as you would see in mil-spec equipment) so I think this is less about what their gear can or can't do and more about warranty issues. If you see where the equipment is used and survives (check out the photo of the frozen camera in this post on CPN) it's obvious that the cameras can take a lot of abuse outside of the "working range".
On the 40mm issues, that's a really lousy response from Canon. While it is "a" solution, it's very unreasonable, and I think that's really poor customer service. The response should have been, "Send in your camera and lens and we'll calibrate them together."