I'm not saying referral hiring is executed well. It's really poorly executed. When I look at the data of companies I've hired for and tracked the success rates of referral hires, they systematically perform better than average.
The difference to employers might be moot I suppose, but if you want to substitute referral for standard hiring screens you kinda need to get at something like this to know if referrals are contributing any new information or just boosting hit ratios on existing tests.
No2 is usually formed by a good understanding of how a company measures success in any given role. You'll find the same principle applies to good recruiters. The more a recruiter understands about how your company measures success, the more likely they are to submit candidates that will pass your interview process.