[TeMPOraL]

Right, and even if GPT-3 could summarize the thousand-line diff in a sensible way, without introducing any falsehoods, it would still be strictly worse than the developer writing a sentence explaining what they think they've accomplished with the commit.

It's just the same thing as with comments and "self-documenting code". The code tells you what (and if written carefully, it may be even somewhat effective at it). It can't tell you why. Neither can a GPT-3 summary of it.

[hgsgm]

I dunno, I'd like to see if GPT agrees with the author's assessment of what their code does.

[funcDropShadow]

But that is neither the purpose of a commit message, nor is it the why a commit was made.