Needs to be explained "somewhere".

Possibly, we are already overdue needing a specific section on netcdf save+load,
analagous to https://scitools-iris.readthedocs.io/en/latest/techpapers/um_files_loading.html

NB this info is currently hidden away in the "developer docs", which was not the original intention and might need changing : see #4990

List of documentation areas that may need addressing

• "extra" specific section, as noted above, on attribute handling in netcdf save/load
• Further topics - Metadata
  details exact metadata members - so 'cube' details need fixing
  It looks so far that nothing else needs enhancing, so long as it's obvious that local+global attrs will now operate independently.