Application won't be returned for the reasons mentioned on this thread. I know of more than 10 cases, including mine, all made the same error, and application was accepted because at least one box was checked, and the table following the check boxes made it clearer.
Scanning both sides of an ID is a must. Also, you're right, several applications do get returned for missing check marks, however those are for questions like whether you've held a SIN, failing to provide the SIN, or consent for IRCC to retrieve CBSA records etc, because IRCC cannot process the application unless that information is provided to them.