I have mixed feelings about the 13" rule. I believe 13" was the pick because of the "average" distance between ear tips when the deer has his ears n the alert position. Like Mohawk, I have seen bucks taken that were plenty mature by age, but failed to make 13", usually going between 11 1/2" and 12 1/2". Possibly the area had a dominant genetic trait that caused them to max out less than 13". 13" seems arbitrary to me science-wise, but the easiest visual judgment-wise on a live deer.
The idea of shooting a spike because he is a spike to rid the herd of spikes can run counter to the objective. Drought, injury, or youth can cause a deer to be a spike that in the years moving forward will produce forked antlers. Other than spikes on the head, the hunter could/should look for other body features that can indicate youth, or maturity such as body shape, presence or lack of a "roman nose" appearance etc...