Reach4
If a hose can be attached then a vacuum breaker is required. If someone putts a hose bibb adapter on the end of the sink spout it must be removed or they must put on a vacuum breaker. You could do it, until you get caught or poison yourself.
In the case of a multi story building it is especially important. Since 9/11 most every municipality has required RPZs on businesses, but vacuum breakers are still required on hose bibbs, ice machines, dish machines, etc. etc. The RPZ protects the source but the vacuum breaker on the third floor would prevent that water from backing up into the water line and being drank on a lower floor or somewhere else in the building.
Stores sell things that people will buy but that does not mean it is going to meet code. They sell bell traps at the local Lowe's, I don't know anywhere they meet code. A hose bibb or sillcock with out a vacuum breaker is OK on a rain barrel, otherwise you might not get enough flow. So there are legitimate reasons to have them and you can always put on a vacuum breaker.
To answer your question about the hose bibb vacuum breaker, sure he could do that. I would install them with an allen screw and not the break-a-way screw or just not include the screw. With water gravity flowing out I am not sure if it would all drain out with a vacuum breaker in place.