Significance of sequency ordering in Walsh-Hadamard matrices
There isn't much significance. Except for few very particular applications like auto-focusing where you might try to adjust the lens such that the higher sequency components has maximum magnitude.  The FFT of a particular sequency isn't bandwith limited. Therefore sequency has very limited meaning.
You should indeed be looking at the applications like random projections, locality sensitive hashing, associative memory and neural networks:
WHT applications