That's not the question. The question is, what was promised, not what can you can you twist their promise into if you choose different definitions than they do.

That's not the question. The question is, what was promised, not what can you can you twist their promise into if you choose different definitions than they do. They have only ever promised that code written in Go 1.0 will be forwards-compatible, not that the build systems will all be the same. When I promise my kid that I'm "taking them to the park" this weekend, they have no grounds to complain when I don't take them to a full-fledged amusement park just because "taking them to the park" would technically cover that too.