The commenter you're replying to can chime in here for an accurate response- but I assume what he's referring to is that a company usually assigns you a fresh, internal GH account. My past three jobs have all done this, which makes it even harder to demonstrate the work I've been doing to employers... Especially when after leaving a company my GH profile is terminated.

This can easily be manipulated - people are literally writing scripts to do regular but random commits to private repos.

I feel like companies don't use Github as much as individuals. I've seen Azure DevOps used a lot, Gitlab right behind that, Bitbucket as a third option, however I've yet to work for company using Github organizations. And I don't blame them tbh, Github for organizations, has less feafures, but costs a ton more than other alternatives. Other thing i've notices is that sometimes, bigger companies have special deals with Microsoft, that for example include some Azure DevOps features for free.