Appreciate your input. Perhaps it is seen as a waterfall way of doing a things. Personally I would write it alongside building the system, then continue to evolve it as the architecture matures. It does not need to be a case of writing everything down first before building things. Although it might be cheaper to change the words in the document compared to destroying Infra and rebuilding it!

This can then be used to show customers or auditors that we have been diligent and designed the system carefully, even if they find some flaws.