You have shown no such thing. You are not comparing like for like across the tables. An increase of 1 strict member would be equivalent to an increase of 1.06 (or thereabouts) of a weak member precisely because they measure different things. You only produce a statistical anomaly by forgetting the difference between the two during the calculation.
Your conclusion that 'a JW who reports field service at least once a year' is necessarily a 'strict member' is rubbish.