FYI: The Symantec support analyst was able to reproduce my issue although I'm trying to verify whether he manually ran a PM import or let the schedule kick in like I've been doing. It appears this issue is consistent on my server whereby if the import task is in a "pending" state due to a schedule I set, enabling or disabling the PMImport checkboxes without first eliminating the pending state will result in your checkbox settings reverting back to what you had them set to.
As a workaround, I had to stop the pending scheduled import task (think we deleted it too afterwards), set the checkboxes to my liking, saved changes, then recreated the import schedule. When my PMImport automatically ran the next time, it retained my checkbox settings. Roman mentioned these settings would revert back if my import was running although didn't think a "pending" status met this qualification since the task wasn't actually running but the "schedule" was pending.
Also, as an experiment, I had all 3 checkboxes enabled but disabled them yesterday while my import task had a "Pending" status. This morning they're all checked off again which confirms that you can't have import status even in a pending state if you want to change any of the checkboxes. If you had enabled the checkboxes BEFORE setting your schedule then you'd be OK but as things would have it, I did just the opposite and discovered this issue.