This setting lets you silently sign in users to the OneDrive sync app (OneDrive.exe) with their Windows credentials.
If you enable this setting, users who are signed in on the PC with the primary Windows account (the account used to join the PC to the domain) can set up the sync app without entering the credentials for the account. Users will still be shown OneDrive Setup so they can select folders to sync and change the location of their OneDrive folder. If a user is using the previous OneDrive for Business sync app (Groove.exe), the new sync app will attempt to take over syncing the user's OneDrive from the previous app and preserve the user's sync settings. This setting is frequently used together with "Set the maximum size of a user's OneDrive that can download automatically" on PCs that don't have Files On-Demand, and "Set the default location for the OneDrive folder."
If you disable or do not configure this setting, users will need to sign in with their work or school account to set up sync.