Aviation security requires airport handling staff to ensure the same person boards a flight as the one that checks in. Simple.
Whether the agent in TFS gave a quick glance or not, you don't know what information he may or may not have actually seen.
Where i work, there was actually a situation whereby the person trying to board the flight was a completely different person that checked in. Luckily the agent on check-in was the same person boarding the flight. The person that checked in was male, the person who tried to board was female! Out of nearly a hundred passengers on the flight, the agent remembered the person and raised the alarm immediately without question.
Also remember that as a boarding agent, its not easy having passports and boarding cards thrown at you (I'm not saying this was you) and trying to juggle everything in quick time. One pair of hands each human being has. Trying dealing with your average family of adults and kids and having 4 or more passport thrown at you.
It makes life easier if each passener has their own passport held open ready at the photo page, and then hands over the (correct) boarding pass for the agent to inspect. Makes life easier for everyone.