I think this takes some time. It takes 2 years of constant practice to learn how to walk well, and we evolved that capability. Learning to hover and fly might similarly take years. He most certainly could do it, but at significant risk of breaking bones and wrecking his equipment and/or starting on fire.
But if there's no ground effect in those videos, then he can already hover. So if there's plenty of footage of stable hovering at 0.5 meters "in mid air", why is there none at all of hovering at 3.0 or 5.0 meters? It doesn't entirely convince me that it can be done.
For the same reason that just because you can balance on a balance beam 30cm from the ground, you'd probably be hesitant balancing on one 5 meters off the ground.
Arguably, the leg-mounted jets COULD be close enough for ground effect, but they're apparently destabilizing so they switched to two backpack-mounted engines instead.