There's a difference. There are rules when playing D&D that spell out what the PC can do and encourages improvised actions, perhaps with a chance of failure. Perhaps it means stretching what your PC can do normally or creatively utilizing resources like using A to accomplish B in a way not negated by the rules but also not spelled out. Then there's doing something explicitly and clearly covered by the rules. Then the DM allows a 30 foot vertical jump when according to the rules that's more than double the max any normal PC could do. It's grappling a creature more than one time your size and, because of how you described it, also making it prone with the same action, effectively turning the grapple into restrained for no reason other than "it's cool". It's looking at the rules and saying "Nah. I'm just gonna ignore those silly rules completely because it sounds cool."
Of course it's not "impossible" in our imagination, but there does come a point where it is impossible according to the rules of the game. There's nothing wrong with throwing out the rules of the game and letting narrative drive the game if that's what you want, even if I may question whether D&D is the engine you should be using. Just be up front about it before the game starts because it's not for me.
