Matthias G. Mayer comments on Basin broadness depends on the size and number of orthogonal features

[Matthias G. Mayer]

Two features are orthogonal if their $L_2$ norm is zero

Just as a side note about terminology: It is a bit imprecise that you use innerproduct and norm interchangeably.

Innerproduct is the function $<.,.>:H\times H\to R$ and the norm is $||.||:H\to R,x\mapsto \sqrt{<x,x>}$