No, they have an accepted meaning among practicioners of that art. That meaning is not more "real" than other meanings, though is more likely to be contextually appropriate. The fact that "reduce" is a term of art in programming for "debug" does not make somebody who uses it in cooking instructions wrong.
Basically, what I'm saying is, the fact that you and your friends use a word a certain way doesn't automatically invalidate other people's usages. It is true that mattmanser's use of "steal" was not legally precise, but neither are many colloquial uses of the word ("It was such a steal at $5!", "He's stealing third", "Great artists steal", "His identity got stolen", etc.). You would be right to object if he had been raising a legal argument based around the concept of theft, but he wasn't, so it seems overly pedantic to me.
> No, they have an accepted meaning among practicioners of that art.
You are getting close to the point here.
Why does a term of art have a specific meaning to a practitioner of that art? Answer that, and you will have determined why words have meanings in any context.
It makes it easier for the practitioners to discuss their art. Jargon is useful if all parties understand the concepts and the forms (words assigned to the concept) used to represent them. Otherwise you have to expand the jargon into larger units.
Borrowing words across fields (because of similarity) can cause confusion. One person may assign a meaning from a different field than the other interlocutors are using.
Basically, what I'm saying is, the fact that you and your friends use a word a certain way doesn't automatically invalidate other people's usages. It is true that mattmanser's use of "steal" was not legally precise, but neither are many colloquial uses of the word ("It was such a steal at $5!", "He's stealing third", "Great artists steal", "His identity got stolen", etc.). You would be right to object if he had been raising a legal argument based around the concept of theft, but he wasn't, so it seems overly pedantic to me.