Maybe you think they mean a literal physical barrier. I think the question is a euphemism for a more forceful approach to securing of the border. When you hear someone say Illegals will use taller ladders, you are listening to someone that will always find a reason securing the border is not possible.
And I agree with you, we do not need to literally fence the entire border. Drones are amazing versatile little critters.
Yes I believe some of them were saying this; a actual physical fence the whole way. That is what made me cynical. The ones saying that are just posturing in my opinion; they know it would probably never happen.
And by proposing one; they are not serious for that reason.
A serious proposal to close the border would involve getting the right people in place and would happen very fast.
I honestly am skeptical that any of them would really actually seal the border.
They will say the right things in debates and other formats; but if elected would they actually do it?