I hate to break this to you, but as you may already know, Nintendo America doesn’t develop, they just localize and do marketing. The games are made in Japan and in Japan there is indeed a game called Super Mario RPG2 that was renamed Paper Mario in America. Japan calls the shots.
Another clue is that Mario and Peach character designs in this remake are in the “cutesy form” which is basically a 3D form of the 2D Paper Mario character designs… so one can assume that they chose the character design choice for this remake with Paper Mario in mind