Asking the real question

How would you know that is what falling from high altitude feels like to be able to declare that your body successfully replicated the feeling to start? You know that it “feels like falling” because you have fallen at some point, in some way. Otherwise you wouldn’t say it felt like falling, you’d say you felt an odd sensation. If you’d never fallen, woke up, told a friend, then they said: “that’s a falling dream” then you realized that is what falling felt like, then finally had your first fall, felt that, and said “wow- that was what fallin felt like. I wonder how I knew?” Well... you’ve very likely had a sudden change in elevation at some point that you didn’t remember concuously, such as being bounced or “flown around” as a baby or some such, or, recall that the senasation of falling is one that is generated by certain stimuli telling the brain you are falling. You don’t have to be cognizant as it is an automatic response. Your brain knows what that feeling is. You’re pre wired.

well dont you only feel the immediate fall? like not the full rush?

Ok but why could I feel my leg rip open in one nightmare

Our brain can process a lot of things which we have not experienced, thats what subconcious is all about.

Rollercoaster unless you've never been on one before is like falling

You most likely have. The sensation of falling isn't excluded to just high falls. You probably tried to walk once as a baby and failed miserably.

If there is anything that encourages a healthy fear of heights it is from falling off a building in a dream and waking up in your bed hitting it as if you were falling.