Piece of advice. Youtube is NOT the place to learn new "theories".
Well it can't be worse than everything on The History Chanel being about Aliens. Did you know, every historical event we've ever had, might have had extra terrestrials?
Is there any reason why this new theory doesn't work?
I wouldn't call it a theory, I'd call it a brain fart with really dramatic music.
I assume you know quite well how your car engine works. The pistons go up and down (or at some angle if you have a V engine, or sideways if you have a horizontally opposed engine). Your crankshaft is then driven in a purely circular motion, centered on the crankshaft main bearings mounted in the engine block. That drives your cam sprocket (for an overhead cam) or lifters, and also your fan belt, and possibly accessory belts.
That's what you think you know. (insert dramatic music with chanting choir). Once you take your car out on the road, those motions are false, because your pistons are moving up and down as you travel down the highway at 88 mph, so they're sine waves, and your crankshaft turns in a helix. But then you go around a turn, so the motion is even more complex! And as you go around a turn, your car tilts a little, and then you hit a bump.... So the crankshaft bearings can't possibly explain the incredibly intricate curve followed by the crankshaft, and thus can't explain the motions of the pistons, much less the intake and exhaust valves.
There must be unknown, magical forces at work.
Or a complete idiot making videos with really cool, ominous choir music.
ETA: I think the trouble your having is with seperating motions based on influences. When a body is subject to gravity, it accelerates, as does everything around it, since those things are subject to the same gravitational field. If you were holding hands with a bunch of people in a space ship and gravity suddenly changed, you'd still be holding hands, and wouldn't even notice any tugs or yanks, and wouldn't notice any forces from the floor or ceiling, because the spaceship would feel the same pull.
You, your friends, the ship, and your breakfast trays are all moving together, and though your course might change due to gravity, it affects all of you at the same time, and all equally, so that you actually have absolutely no way to detect that anything changed.
This is different from a car on a bumpy road, a train going around a curve, or an airplane flying trhough turbulence, because in those cases an external force was applied externally
to wheels or wings, not to the occupants directly, so they slam into the seats or doors. Gravity isn't like that.