Reg, your probably quite right, but how many anglers would have the confidence to try something as bland as a bare hook with just a bead? Most prefer the safety blanket of a box full of angler catching creations!
As a relative novice to salmon fishing, but someone who fishes for almost everything, I have a very open mind with regards to methods and tactics.From my limited, but revealing observations, the key to inducing a follow/take is not pattern ,but how the nymph catches the fishes attention, dropped onto its nose and then drawn away upwards works, but far better to bring alongside from behind its head then up or outwards from the fish(long rod),Obviously not touching the fish with the line/fly is vital. As for size of "fly", having had takes with things as diverse as 6inch redgill sandeels(try them!) and size 14 nymphs with a pink, metallic tungsten bead head(deadly) , whatever floats your boat.
peter