I am a former roofer, and have replaced hundreds of roofs. Got me through college in the 70’s.
It is not possible to check every shingle tab for proper fastening, so why write up the defect, especially if the roof is over 10 years old, and no missing tabs? An attorney will ask that question. Temperatures have to get up to at least 100 degrees to seal the tabs. Many northern areas never reach these temps, so they may always be loose. This also can be an SOP issue, as we do not (at least most of us) will not move or dismantle anything to inspect the item/area.
That is a good narrative, Sean, but care should be used here, when a roof replacement can run into the tens of thousands, and the home seller will scream at your findings. You will then cause the buyer to walk, the REA to loose their commissions, the mortgage company to loose their revenue, etc. etc.