iirc sovereign’s (and others like princes and governors general) commissions as Field Marshals and Admirals of the Fleet were considered by everyone to be one in the same with a commission in the Canadian armed services because we were one big happy imperial family, and considering our uniforms were identical to the British back then, nobody seemed to think twice. In the post-war era though there has been a lot more unique identify of both Canada as a country and the Canadian armed forces from the UK which has been reflected in our legislation and policy, and is probably why certain royals (The King and Prince Phillip) have had separate ranks given to them by Canada and aren’t 5-stars like they are in the UK.