Given Gord Miller does mention this rule from Lou Lamoriello has some wiggle room, it's hard not to assume that if Horvat explained his reasoning, that would be good enough to keep number 53. Maybe Lamoriello forced Horvat to change his number, or Horvat was open to a completely fresh slate with his new team. However, it does need to be considered that 53 is also currently worn by
Casey Cizikas, so perhaps Cizikas wasn't comfortable offering it up or perhaps Horvat simply didn't want to come in and take someone else's number.