Every game is going to have some degree of outsourcing. Every single one! What makes the game an EPD game is more if they are the lead developer on the project. Some games have 30 EPD developers (Pikmin 4, Miitomo), while others have 100 (Splatoon 2/3, ARMS, Animal Crossing). Tears of the Kingdom featured the biggest pool of EPD staff (200). The rest of is always going to come from other parts of Nintendo (MC, SRD, 1UP, NST, NERD, Monolith) and outside companies. If DK had a 30 man EPD staff spearheading the game and the rest of the team came from outside companies like Pikmin 4, it would still be and feel like an EPD game.