This is where information governance comes in. It's fine to add bespoke profile fields in SharePoint (or any other app), and the Identity hub is will just igno

This is where information governance comes in. It's fine to add bespoke profile fields in SharePoint (or any other app), and the Identity hub is will just ignore them if it's not got rule defined. If it's decided that the 'favourite animal' field is to be pushed out to other apps, then a new rule is added to the Identity sync process. It's all fail simple as you say; the main problem always tends to be departmental politics.