From top to bottom, the gate is very rigid. From side to side, the gate can bow a little since it's secured at 2 points: the hinge(s) and latch. This bow is minor and only for a few inches. To answer your question... nobody is going to get under the gate and above only matters on the size of the opening (to structure) above the gate.
Our gate covers a sliding glass door, only a cat could get thru. Fwiw, the bars that form the scissors are square tube steel which makes them very rigid! They will not bend. This is a good design.
By Swede