Yup that's what curious droid's video on this is saying as well [1]. Basically the plans all were off a little bit and each rocket engine was hand-tailored to t

Yup that's what curious droid's video on this is saying as well [1]. Basically the plans all were off a little bit and each rocket engine was hand-tailored to the demands of the individual rocket by these skilled people you mentioned. They did document their changes but only on scrap notes that since were lost. The plans themselves that were archived don't contain those notes and even if they had them, you couldn't find people with such skills any more. [1]: https://www.youtube.com/watch?v=ovD0aLdRUs0 https://www.youtube.com/watch?v=ovD0aLdRUs0