That's not the point.
Cook played nine. I don't see anyone naming him as our best hooker yet he's one of the top 5 hookers of all time and second best in the league atm.
Everything is what it is but at the same time it is what it's not, or what it's meant to be or never was.
Fact of the matter is Lamb is/was a 9, without the number on the back in 1985. The games evolves and Lamb would too. Lamb is equivalent to a Smith or McInnes and the modern day half has a different role, kicking and organising backline etc. whereas lamb is organising the team and has instincts from dummy half. It's all about the modern interpretation of an old player. Not everything is straight forward and the best wingers are now fulllbacks, but are now being replaced by specialised big wingers.