Mmk yeah. For practical fish-keeping and housing, bigger is definitely better. (And honestly, I think we've both seen 1/2 gallons being the end of the world for bettas - again, with those certain people who don't care for them).
I know how to back the "DON'T DO IT" thing if I weren't sick and could focus properly. Maybe not entirely back them up, but there's reason behind it.
Like the people who say "never do it", it's a bit shallow and doesn't properly explain why, but this is always said to the brand new fish owners who want an easy (emphasis on easy) pet fish to care for in something that doesn't take up much room. "What? Daily water changes? Whatever." Of course there are people who ARE willing to do it, but for me, I'd usually avoid suggesting 1/2 gallons because some (more ignorant) people just take it and go. And especially through the internet, you don't know how they really are and their dedication to the fish. I know one person who could probably make the 1/2 gallon work. But for the people over the internet, it's doubtful you would realize that trait in my friend and care more for the betta. Which makes sense in how I see it.
And yes, it would be more senseful to explain why someone shouldn't use a 1/2 gallon.