Finally completed Brainiac Marzia, tried to take screenshots that might prove this. I have 4 in-game and 1 snippet.
Screenshot (1): All numbers input correctly, pay attention to math notebook number.
Screenshot (2): Brainiac math notebook 1/10 on language level.
Screenshot (3): Math notebook collected, back at completed elevator.
Screenshot (4): Language level win screen. Especially yellow text.
Snippet: Zoom in to see close times of previously taken screenshots and those exact same screenshot images. Month, day, year, hour remain the same, minutes are close to each other. From 5:23 PM to 5:28 PM for previous screenshots.
MIX had a livestream where he showed that Marzia stops after inputting all correct numbers in elevator, that's how I took these without much trouble.
Sorry for long post...just find it hard to prove that it was on Brainiac difficulty (since language notebooks have no significant change nor elevator number range), Viktor's notebook was one thing people could notice, so I went with that.
I already wasted enough of your time.