However, it's not in the POH, if it is so crucial why does it not exist as part of pre-start in some schools and does in others? We have one school of thought that says no practical reason not to follow the POH the other school of thought that creates double redundancy and unnecessary 20 minute run-ups.

niwre wrote:However, it's not in the POH, if it is so crucial why ....

False dichotomy. It's neither crucial nor valueless. Therefore it's included by some but not by all, as you might expect.