An unexpected plot development is not a twist

Following up on another similar thread about plot holes... I am always bugged by people referring to things as twists, when they are simply story beats that you may have not seen coming. A twist is when the audience is holding on to a truth, and then you find out that the thing is not actually true.

A character suddenly being killed at the end is not a twist. Finding out that a character you thought was dead is actually alive is a twist, because you were lead to believe they were dead.

I've seen people refer to the ending/escape in Shawshank redemption as a twist. No, Andy escaping is a plot point, just like Brooks being released and Red getting denied parole were. It might be a surprising plot development you didn't see coming, but it didn't take a key truth that you held to and suddenly show it to be not true.

The truth you are holding to could be explicit or implicit. In Star Wars, you are told specifically by a trustworthy character that Vader killed Luke's father. Therefore finding out that Vader did not kill Luke's father is a twist. In the Sixth Sense, it's implicit, because the main character being alive is just something you take for granted when watching basically any movie that doesn't specifically tell you otherwise.

But "the main character won't die at the end" isn't an implicit truth that you just assume. Maybe it could feel that way if you've never watched a movie where the main character dies. But people dying is normal; it happens in real life and in movies.

There's room for some grey area I think. For example "the bad guy wins" has some room to be called a twist, though I personally normally wouldn't.