The only thing McDougal will accomplish by entering both the 5K & 10K, will be to lose both. He probably couldn't beat Rupp and Rohatinsky anyway, and he certainly won't beat them having run a 5K semi-final the day before. Then when it comes to the 5K finals where McDougal would normally be expected to win, he won't because he will have likely run a very hard 10K the day before.
No one can fully recover from a 5K or 10K race within 24 hours. Some runners have doubled at NCAAs and won both the 5K and 10K -- but they were a big step up from their competition. McDougal isn't and I don't think Sally Kipyego of Kenya/Texas Tech. is either (at least not this year).
There is an old stock market adage that goes something like this: Bulls and Bears will each have their day, but Pigs always lose. In going for two NCAA championships, Josh and Sally will get none. Galen Rupp & Amy Hastings win the 10K and Chris Solinsky and Molly Huddle win the 5K.