How much of code review friction comes from context outside the codebase?

I analysed 10K open-source PRs for something I'm building and found that anywhere between 42% and 67% of review friction is due to context beyond the codebase.

From a workflow PoV, how annoying is the manual context synthesis to curate the prompt/agents.md? Is review a solved problem for teams with review agents, or is it now the real blocking step?