I'm referring to the fact that "open source" quite literally means "readable by humans [and machines]", and anything beyond that is a subject of debate. There are more users than readers in nearly all cases, but being able to read the code as a user is a significant benefit at times, and it's one of the reasons it's such a large ecosystem in terms of both users and contributors. (it usually being free is another big reason, of course)

Even with coding agents gaining popularity, many humans still look at the code at some point.

I see. That depends on how much I care about the project. My favorite ones get weeks of review and refinement, to the point I still consider them to be more or less hand written. Not all projects get to be that important.