they refers to more than one person while player refers to one person - you can only use he or she when regarding the player. "it" is kinda awkward when used to refer to humans so it's unused, but "it" when referring to a pokemon is fine (neutral-gendered).
At least that's how I interpreted it; I wouldn't add he or she to just the pokemon, but in that case it would have to be consistent across the entire analysis, meaning no "it", right?