QR systems are poorly equipped to deal with such seat reservations on the different aircraft that they temporarily lease from other airlines. That is not unexpected for any airlines.
But if you look at Expertflyer, they are quite a few assigned in that section (row 30 to 34).
If the agent say that they are booked, they probably are, although they do not show on the QR system accessible to pax.
Just check on EF if your seats show as asigned.