Yes, you get people fixing each others' typos. This is rather wonderful... rather than demand perfection from people, and punish them for making mistakes or not having all the right knowledge, it turns this to advantage. People complement each others' weaknesses and form powerful teams.

This isn't wishful thinking... we see this all the time. The Git history documents these interactions.

It does sometimes make it harder to cherry pick patches to backport to old releases. Yet that's a minor cost compared to the benefits of getting more, and happier, contributors.

Yes, it is, but this is not necessarily a bad thing.

For a detailed explanation, see Pieter's keynote on EuroSciPy 2015 [0], where he answers a similar question around 19:45; however, his entire talk is worth watching because it sums up very well the ideas behind the C4 process.

[0] https://www.youtube.com/watch?v=O8CbzKREAj4