I can't see any overhang on the inside of the cage either, which is what surprises me most since even a young cat could, I think, scale that wire without much difficulty. Unless there's a single strand of electric wire at the top that we can't see.
Certainly big-cat enclosures in the UK are often some of the most secure; often with double wire and very high with overhang and nothing near the edge to allow the cats to jump.