In my prior experience (inside and outside of software, anything having to do with a process) I think there is another situation where diagrams are enablers that they missed. Finding consensus on how the thing currently works.

When these issues are takled about in words, through code, through hand waving whatever - I have experienced that the details often mask ensuring that everyone is on the same basic page. Often when there has been confusion it has taken someone pulling the group back and noting that 'Bob things A is connected to B and then connected to D but Alice thinks A connects to C before connecting to D"

Just putting a architecture diagram of a process up helps find shared understanding.