Oh there is a correct answer to the difference.
When using the traditional innings-based deployment where this deliver pitches the 7th, another pitched the 8th, closer in the ninth, a manager really has no control over the quality of hitters his best reliever faces. But he does in the first inning - he gets the top of the lineup. Every game. Much better than holding on to your closer for the ninth inning, where 44% of his save opportunities start off by facing one of the 6-7-8-9 hitters, who are always the weakest hitters.
Opener strategies create better matchups for the manager. Use a good reliever to face the 1-2-3 and maybe 4, 5 hitters. Then bring in your “starter” to face the middle-to-bottom hitters. Not only more effective use of the bullpen, but also of the starter (or “bulk” reliever) as when he hits the lineup second time through, he’s doing so against the middle/bottom of the lineup.
It is a clever strategy when done right. But again, if you’re using Zack Weiss, you’re just not doing it right…