I noticed the same thing a while ago. I read the chamfer dimension help file and it emphasises (underlined) you have to click the short line first so thats what I do.
I think it would be great if you could click just once and it does it for you if it is a 45 deg angle chamfer.
I have had it work in the past but I just noticed the ability to create an incorrect dimension.
I would still call this a bug. There should be some intervention by the system to prevent the creation of a bogus (highly technical term) callout.
At the very least there should be a clear prompt.
I am a very experienced user and this caught me by accident. I would hate to see a novice get fired for it. This could result in some interesting looking parts if the dimensions were followed verbatim.