Just for info, also what could have played a role, is that you need a mask for the child in case in depressurisation. And only a certain amount of seats have an extra one. So per 2 seats, there's often 3, but not 4. We had that on a flight 3 years ago, I think an embraer, 2x2 configuration, only the right side of the place had 3 masks per row of two.