If there is effacement of comparatively strong (syllable-initial) nasals, then there must have already been effacement of comparatively weak (syllable-final) nasals.
Standardized
IF comparatively strong (syllable-initial) nasals are effaced [deleted?], THEN there must already have been effacement of comparatively weak (syllable-final) nasals.
For a more general statement of the same nature about consonant deletion, cf. #1765.