I believe many manuals are indeed written before the program is finished.
Occasionally you will find manuals that describe features that are not there
or are not implemented right. Some manufacturers plan on having a feature,
but they later found that they encountered problems that they cannot meet the
delivery dates, so they release the software with the feature or with bugs in
the feature. But because of printing costs, they do not want to print the
manual before and after the correction, so you get manuals with errors in it
until they send you a free upgrade.
So when you receive a free upgrade, it is not because they are so nice. It is
usually because the earlier software contain serious-enough bugs that somehow
maybe you did not encounter because you didn't use a specific feature.
About film recorders, most of the earlier models were made for presentation
slides. Someone later came out with the idea of using it for negative, since
the film recorders are able to image to slide with a density range of about
3, it seems like it should be easy to record to negative film where we only
need a range of 1.2 to 1.3 to match RA-4 paper; and oh boy! Were they wrong.
This is another example of how theorical data might not work in real
situation.