Most of the users using ACC will be likely to use ISO19650 naming convention which calls for the first part to differentiate the project name/number. However, ACC Sheets works on the basis that it takes the discipline automatically from the first part of the document name and presumes discipline is going to placed as the start of the document name, therefore, if your project does follow ISO19650 naming convention or any other naming convention that does not have discipline as the first part of the name, the Discipline will not work. If that wasn't bad enough, there is no way to change the discipline manually, therefore if your document name starts with a letter that is used in Designator disciplines, for instance MX5-XX............. it will automatically take M-Mechanical as a discipline because M usually stands for mechanical.
It is crucially needed from Autodesk to address this asap and enable changes by project admins for Discipline field, this way it is unusable.