Just because you can't get everyone to agree does not mean that the concept is not well-defined or clear. People can and do disagree over almost anything. That could just mean that one side is wrong and the other side is right, even if it is difficult to determine which is which... or simply difficult to navigate the underlying politics regardless.

Besides, in your example, either kind of gap could be a bug or a missing feature. It's a totally orthogonal question.

There are some really obvious things that are definitely bugs. If login doesn’t work if your email address contains the letter “e” when the expectation is all valid email addresses should work, then that is a bug. It isn’t “indistinguishable from a feature”. If clicking a button in your accounting software consumes all the RAM on your computer and causes it to crash, then there is no universe or agreed upon definition that would consider that a feature instead of a bug.

>Your argument hinges on all parties agreeing on what "wrong" means

No, it just hinges on common sense. "All parties" are never gonna agree on everything.

There will always be customers that demand whatever and treats its lack as a bug. Doesn't make it a bug anymore than me asking for a free glass of wine with my meal and not being given any is "injustice" - when the restaurant never promised any.

What party would desire to crash a program