I don't know about routine skimming of history, but promo committees in big tech look at both commits and code reviews (the comments you left on others' commits).
I work at a FAANG like company, and here it's just annual performance reviews, that include bunch of achievements and then politics. No way anyone is going to check anyone's commit history. There are huge calibration meetings where managers have to stand up for their engineers on who gets what kind of performance rating and who gets promoted, and it's just verbal debates. There's just no way anyone can bring up someone's commit history and have enough time to explain what is going on overall.
And managers have little clue about the actual work that is going on. Definitely not enough clue to understand what commits are about, even if they have had a technical background overall.
