Try throwing a ball into the air while driving along in a car. Just after throwing it up have the driver turn sharply. What does the ball do, stay within the cars frame of reference, moving with the air mass? Now try doing the same with a sheet of paper, something with less inertia and more air resistance. Same result?
That’s no longer the same discussion. We’re talking about the behaviour of aircraft in a constant airmass. Using car analogies is fine, but once you start swerving around in the car, it’s no longer analogous to a constant airmass.
Why do we think that that an inertial/gravitational frame of reference works differently laterally to vertically?
We don’t.
I think you are all just arguing about the relative balance of inertial to aerodynamic forces. All sort of depends how much inertia you have and how much lift/drag you have.
Er, really?
Eckhard’s post was about the most simple and elegant explanation of all this that you’re likely to read, and should’ve put an end to the discussion. Yet here we are.