I always thought that the frontier coding models were specifically trained to perform well in the harness from their providers. I imagine this will always be the case to some extent.
From what I understand pre-training is totally irrelevant to this and as far as post training goes there will be multiple steps, for claude and codex and the like that ship with a harness, the harness is definitely included in evaluation. However, they will definitely include evaluation from a variety or even none, and settle on something that works the "best" for a release.
Disclaimer: No first hand knowledge
Yes, and the article makes the point that this might be changing.
even if they are is no guarantee that for 'your' specific tasks is beneficial in any means