Hi cf090,
Thank you for your question.
No. you misunderstand, when AllowNonProvisionableDevices = false, it allow mobile devices that dont fully support policies to sync.
In Microsoft, The AllowNonProvisionableDevices parameter specifies whether all mobile phones can synchronize with the server running Exchange. When set to $true, the AllowNonProvisionableDevices parameter enables all mobile phones to synchronize with the
Exchange server, regardless of whether the phone can enforce all the specific settings established in the Mobile Device mailbox policy. This also includes mobile phones managed by a separate device management system. When set to $false, this parameter blocks
mobile phones that aren't provisioned from synchronizing with the Exchange server. The default value is $false.
We could refer to the following link:
https://technet.microsoft.com/en-us/library/bb123756%28v=exchg.150%29.aspx
If there are any questions regarding this issue, please be free to let me know.
Best Regard,
Jim