I think it was mostly a case of little brother following big brother. As soon as Grant went portal at Northern Michigan, Hammer was right behind him. Grant didn't light it up right away in the USHL until he got into his third year, and by then he had already committed to Potulny.
I can't imagine being Warroad kids that UND didn't at least put a call out when Grant went into the portal, but I don't know.