The high ground was just a ruse. Obi Wan has the advantage on the low ground. Vs Maul and Grievous, he attacked from below. Taunting Anakin about the high ground was just to make Anakin try to get the high ground so Obi Wan could attack from below. Which he did.

Attacking from the low ground in melee combat is advantageous as you can just go for the ankles, as my niece figured out very early on when we used to play lightsaber battles. She’d insist I stand on the bed, and she’d slice off my ankles, it’s over, Auntikin, I have the low ground, haha.

I don’t get it