Well, maybe.  The general idea is that eating the same thing every day emphasizes food as nutrition, not entertainment.  When meals are less exciting, we’re less likely to overeat.

The caveat: mix it up to avoid both nutritional deficiencies and bingeing when the boredom gets to be too much.

Here’s an interesting POV on the subject: https://www.healthline.com/health/eating-the-same-thing-pros-and-cons