Nah, not at all. I’d say true almost never.

Great point, but you’re completely wrong

The word can mean that, but usually it signifies a much lesser degree of contrast.

You missed the perfect joke even if the author had no idea what they were doing

Like, that's the literal definition of "but." It means that you're about to say the opposite. Otherwise you'd use "and".

People, like Cuban in this instance, use it to preemptively defuse [mostly in their own minds] the real portent of what they are about to disclose.