I think the point that he is making is that the additional friction is a good thing and necessary in this case because it's an open source project. It's too easy to do drive-by PRs that don't actually provide value and just eat up review cycles. The issue requirement simply ensures that the requester actually is invested and cares enough about this to get approval before starting work on it.

I can see why that doesn't sound great particularly on a team where everyone knows each other and is working together but it totally makes sense for me if I were maintaining a project that was large enough to get a lot of low-effort PRs coming into it.