I can’t tell what code in that link you are referring to, but it sounds like this is highlighting and example of overfitting.
With only 100 observations, it doesn’t take a very big model to be able to fit to any output. Normally, you would have a separate hold-out dataset to test the model against. If you are fitting random inputs to a random output, your model will fit your training data very well, and will not fit at all when tested against the hold-out data.