I think the counter-argument is that "curl" is a project maintained by Daniel. If you are going to ship a product that doesn't behave in the same way you should call it something else. So Daniel is right about what "curl" should do, but Apple can be right about what "applecurl" which is very similar to curl should do.
I think parent doesn't mean Daniel is never wrong even without proof but if one side claims a bug is a bug and the other says it's not than you can pretty sure it's a bug if Daniel considers it as one.