Yes. He was also a M-W RL junior. During the 13 import rule era, when he was playing for Manly, he was listed in the Big League programme as a local junior. Imports had an a asterix next to their name. That means that after turning 15 (in his case around 1963-64), he must have played at least two full seasons in the M-W junior league, under the rules defining what constituted a local junior.
Relaxation of the import rule to allow long serving imported players (i.e. Graham Eadie) to be classified as 'local juniors' only came into force a couple of years after Knight's retirement in 1979.
Hope that clears it up. And my apologies if that additional advice falls into the 'suck eggs department'.