ok i think i know what's going on
using UTMT, i managed to find the message (it's actually "I AM STUPID PERSON").
it seems that if the game detects that either controller port has an axis deadzone, the thing that determines how far the joystick has to go to detect movement, set to 0.25, the game will show the message.
i even tested it out, starting the game with a controller, and this is exactly the case. this message showed before it took me to a controller set-up menu (the image is offset, weirdly)
you can fix this by not using a controller at all or just changing the deadzone.