Hi! Thanks for playing my game! It's nice to see people appreciating my game, my first ever real game 😅
Now, to answer your questions, yes! The characters not being affected by the way you treat them(giving or not giving them food and drinks) and the tutorial that tells you that you should treat them nicely are the "instructions are a lie" part of the game.
The main goal of the game is to understand the story of each character and based on the dialog with them to poison the thief and keep the traveler's chest safe.
Thanks for the feedback!