This is not the case and the maintainer outlines why. (1) FOSS means you (the "licensee") can do what you want with the code, not that I (the "licenser") am so

This is not the case and the maintainer outlines why. (1) FOSS means you (the "licensee") can do what you want with the code, not that I (the "licenser") am somehow obliged to take your input on it. If the maintainers find that code contributions are reducing their maintenance effort, which is often the case, then sure. But if on the other hand reviewing the contributions themselves _increases_ effort, then it literally is a net-negative to accept PRs. (2) It's also very possible that PRs create extra work. Sometimes reading and understanding someone else's solution to a problem is harder than coming up with your own! Of course, one could take a laissez faire approach to maintenance and just assume good intent and do light reviews, but that doesn't necessarily make for a better codebase.