It’s not clear why you’re taking about warranties.
It’s strange to suggest that bad code is good because it provides a chance for others to fix it.
It’s also obviously not true that if developers wrote great code the first time we wouldn’t need open source.
On the contrary, that would make open source far more valuable because it would be easier for people to add to or modify, and a better example for newcomers.
The author is not attacking the existence of open source. He is saying it is necessary but not sufficient for empowering people.