To check my understanding

Is the motivation for the closer to

1. using sendfile() will break $X, and we know X
2. there's high probability sendfile() will break something
3. there's unknown probability sendfile() will break something
4. there's low probability sendfile() will break something, but it is still too high
5. any non-trivial change here is too risky, regardless of sendfile()
6. something else?

My guess is 5.