To be frank,theres an difference between regular outsourcing and what nintendo support studios do, on Odyssey and Botw Monolith/1-Up artists are credited for Landscape
Art, where the outsourcing companies got credits for Landscape
Modeling, one is a creative position,the other not, those outsourcing firms strict follow nintendo orders,they finish assets based on concept art and art direction, Monolith and 1-UP are actively involved since the beggining phase and have creative input on the project,theres entire Splatoon stages comceptualized and made by Monolith alone, 1-UP designed a lot of Odyssey characters and worlds, heck, the chief concept artist of the game was from 1-UP,if you look the artbook most of the art presented was drawn by Asami Inoue from 1-Up,all the art bellow is by her
Monolith also had their own ideas for furtinure and clothes for animal crossing