I think the frame of reference is the programmer intent. If he/she intended to check for equality but wrote:

    if (x = 42) {

Then that is most certainly a bug.

If a bit of text was supposed to be blue but came out green, maybe because the person writing the requirements doc got it wrong, it is hardly a bug in the code. The code is doing what the programmer intended, even if that is not what the user wanted. That's why the world has moved on from "bug trackers" to "issue trackers".

> There isn't much point in rejoicing over the code that correctly implements an incorrect design!

And there isn't much point blaming a coder for correctly implementing an incorrect design, especially if the design document is all they have to go on.