I say "sort of" because if he's truly concerned about the effort involved in creating independent implementations, then obviously he should be evaluating features by the difficulty involved in implementing them. typedef and typeof are absolutely trivial to implement [0] [1]. typedef just creates type aliases and typeof is very similar to sizeof.
Also, I'm not sure what 1000 functions you're referring to, but most functions being added are already in POSIX and already exist in a huge number of independent libc implementations. There are dozens of POSIX libcs, including at least 5 totally independent implementations for Linux alone that are still fully maintained and under active development.
[0]: typeof: https://github.com/rui314/chibicc/commit/7d80a5136d1b2926dd0...
[1]: typedef: https://github.com/rui314/chibicc/commit/a6b82da1ae9eefa44da...