The source’s explanatory note states that if the response is “huwa hurr” or “aw huwa hurr”, purchase acceptance is not implied in the same way. The connected succession that supports the earlier implication is absent.
“Fa-huwa hurr”: connected answer; implied acceptance in the specified case.
“Huwa hurr”: lacks the connecting fa; acceptance is not automatic.
“Aw huwa hurr”: uses an alternative particle, not the same implication.
Changing the particle can change the legal reading, even while the main predicate “free” remains unchanged.