The Lone H Lore

LORE: The Lone H, who has the power to understand Pokémon, doesn't catch them in the typical way. He befriends them after an important, sometimes life-threatening situation. He sometimes attempts (and fails) to learn Pokémon moves, and agrees to battle random wild Pokémon directly to help them get stronger. One day, he met Silver, a Shiny Eevee, in much the same way, where Silver helped him by fighting a ton of wild Pokémon when he was in danger. After the whole situation, The Lone H asked Silver if he wanted to come with him, and Silver agreed.

What moves does Haikiri already know btw?

(And about how tall is he?)

Idk abt hight... But he only TRIED to learn Pokémon moves...

Oh, he can't tho?

Obviously not... He's a Trainer...

I mean, trainers can sort of use pokemon moves, or atleast their own versions of them.
In the anime we clearly see Ash replicating them a few times. (Although mostly for comedy) In the earlier anime episodes and some of the games humans can use psychic abilities like telekenisis, illusions, and even teleporting.

And then there's the Let's Go games which introduce 'Special Techniques' which are special moves specifically learned by humans, though we never see a human use any since your eevee/pikachu wanted to learn them instead.