There is a physical limit to kickflipping over something that can be ollied.
The kickflip needs the width of the deck/trucks to pass under the feet, while the Ollie just needs the height of the deck/wheels.
The width is longer than the height.
Therefore, if the height of the jump of the person is equal in all circumstances, it is impossible for the kickflip to pass over the same height of obstacle as an Ollie (at the person’s maximum height of obstacle clearance).
*see the Reese Forbes x Element Ollie Challenge photo above where Danny Wainwright is ollieing your face.
So, in fact, the statement “if you can Ollie it, you can kickflip it” is not true as there are circumstances in which it is false.