Sure, they're different things. The comment wasn't meant to be in vacuum, but as a response to option being a better logic 3-state.
I agree that for other reasons it's better, but conceptually they are used to represent the same thing. (Logic variant of null)
No, it's not.
> Or a "typed null" to be more precise.
To the extent this is true, it is a fundamental difference.
> It's got some nice properties, but really it's the good old tri-state.
No, it's not. Because the Boolean type contains only True and False, not Null and the Option<Boolean> type (likewise, Option<Option<Boolean>>, etc.) does not contain True or False. There's no weirdness in doing logic operations on an Option<Boolean>, or a pair of them, because it is a type error to attempt it because Option<Boolean> is not Boolean.