If it's not literally word for word and organized in the exact same way, it really shouldn't be an issue.
But you are absolutely right, and I don't think anyone would disagree with you, that a clean-room rewrite of the voluminous manual would be prohibitively labor intensive.
But a condensed/simplified manual wouldn't be. For many, if not most systems, it would be as simple as taking the study window textboxes and diagrams and putting in a PDF with headings and a table of contents. For others, it could be simply writing a simplified description "There are 4 pumps. This is always on normally, these are only on as boosts in auto", or literally copy and pasting explanations given in the forums or on discords into a PDF.