You lost me at “pair programming”. Having tests for what you can test is fine. But there’s code that simply can’t be tested, or at least not easily at which point you are just wasting time. Open source mantra is always great in my opinion… release early, release often. In addition to that have a test version of your software before you push it to production if there’s sensitive data. That’s usually good enough to catch issues.
And he’s right, reviewing changes before merge just takes time and resources away from project while the master branch keeps moving. Merge, if there are issues, whoever submitted the change is obliged to fix it. You can always checkout earlier version.