I'll note that only the largest of those companies had this deployment style. The rest were either ~quarterly (with client pressure to slow that down) or weekly

I'll note that only the largest of those companies had this deployment style. The rest were either ~quarterly (with client pressure to slow that down) or weekly/monthly (agile-ish). I think the only one with a formal release process was the quarterly release outfit, and even that was due to single-client risk.