What Cruz has done to collect these “Cruz-friendly” delegates is legitimate. They will still represent the voters on the first vote. Cruz was smart to do this.
However, Trump can always use his money to sway enough delegates back to him, as well.
What is said is that Cruz knows he cannot reach the 1237 number and is just trying to throw the nomination to the convention.
This is against the spirit of the primary system.
Convention fights always leave the candidate chosen weaker and Cruz's actions set a bad precedent for future elections where the goal of the candidates will be just to keep the forerunner from getting the required number so the convention will decide.