> at what size or capacity should you be required to document and publish these things?

The reason there is an opaque number in that open source utility is precisely because of a lack of open documentation for that register definition. Independent black box analysis of the messages only got as far as "write this value to do effect X". Whomever developed that utility would have loved to spell that bitfield out, but not at the cost of more days reverse engineering.

But manufacturers aren't reverse engineering register definitions, they're working off of vendor datasheets or protocol definitions they themselves created. All of this documentation has already been produced, as it was used to develop the tractor from its various subsystems. It just needs to be published!