>>57805742no, you have to edit the starter and partner list in skytemple yourself, which is really easy. you might wanna buff the stats of your new starter/partner because most pokemon are severely underpowered compared to the default starters/partners.
also know that you have to manually edit the script for a specific cutscene at the start of the game to assign your new partner the correct gendered dialogue set. if you dont, every new non-default starter will use the "formal male" dialogue set in cutscenes, iirc.