It's just as easy to index multiple repos as it is to index one, which means that the same goes for searching. Why would it be any different for one as opposed to many?
We use GitLab in the company I work for. There may be repositories created by others in the company, that depend on repos I work on, where I don’t have access to said other repos. So to me these are invisible. If everything was in one monorepo, it’d all be visible to me easily.
That’s more of a culture thing. Your company chose to enforce more granular permissions. Perhaps there are good reasons behind it, e.g. code for different clients being under different contracts and NDAs.
That's a question of policy, not of repo structure. A monorepo can still have certain parts of the repo protected by access control. One repo doesn't mean "all files share one read permission".
