Not quite true. At least from 1982 to 1989, my time with intimate IDF knowledge, every "regular" combat unit I knew of (infantry, engineers, armor, artillery, paras, AA, land and sea sayerot) where issued Galils or the short barrelled Glilon. Officers often chose shorty M16s, and M16A1s were often issued to second line and reserves.
Thank you for the correction. I wonder when the change occurred.