a 10x programmer can generate complex, well engineered systems with a reasonable structure, not by writing everything in low level, super hard code ?

Yeah maybe, but I'm certainly not at that level.

If a 10x programmer exposes foo() and bar() methods to me, I'll call foo().bar() and not realise I've made a mistake, or that I've violated some invariant that's only in his head, not in the low-level code itself.