I bow to your experience, but I can see how technical manuals similar to recipe books could definitely benefit from notes that say "this did/didn't work because

I bow to your experience, but I can see how technical manuals similar to recipe books could definitely benefit from notes that say "this did/didn't work because...". If you've got rubbish colleagues, then yes you've got a problem, but also you could have an excellent record from the old master that just retired. You could keep notes as separate pages in the book, but having the notes in context does appear to have the potential to enhance a manual rather than ruin it.