This is the same in case of an official build: if some attacker was able to modify what happens in a build that makes it to production, I need logs to build an understanding and explain to auditor/governments exactly what happened, what the effect was, and how I’ll mitigate it.

Since all logs should be immediately persisted off box, they are protected from tampering.

Of course there’s no reason the default view of logs in the CI/CD system needs to be so verbose.

I don't think it is. These are both logging devices that you look at after the "incident". Sure there are differences, the CI job is likely easier and cheaper to reproduce to get more data, but at the end of the day you want to be able to figure out what happened by looking at the logs.