Instead, an extremely precise jump is required followed by aiming down to shrink Samus' hitbox.
From a full height jump, there is a 2-frame window which can touch the transition at the correct height,
when Samus is slightly below the center of the doorway.
With HiJump unequipped, the start of the frame window is just as Samus rotates to become horizontal.
Hold forward through the transition.
One frame after the transition completes, hold diagonally down-forward.
See also: Tech Page