Of one my patrons at the Library had been an infantryman in Vietnam. He said that whenever a North Vietnamese fired full auto, they would yell, “Get the guy with the machine gun!” and concentrate fire on him. If an American fired full auto, the Vietnamese would begin yelling, presumably an equivalent phrase.
Bill said everyone fired semi auto.
Also the Commonwealth version of the FN FAL, the L1A1, isn’t capable of burst or automatic fire but is considered an assault rifle nonetheless; so automatic fire capability isn’t a requirement to be considered an assault rifle. Ironically FAL stands for Fusil Automatique Léger (Light Automatic Rifle).
Using that manual’s definition you quoted, the US Army’s own M4A1 isn’t an assault rifle as it isn’t capable of full automatic fire. Mind you the linked manual is from 1973, entitled “Small Arms Identification and Operation Guide Eurasian Communist Countries 1973.”
As you well know when you are talking about legalities it’s important to use precise language. That is the reason in the law they did not use the term assault rifle but instead went with assault weapon with a different meaning.