I believe players like Maruk and Tharp are taking advantage of the "4-2-4"
rule.  By it, a player can transfer from a 4-year school to a 2-year junior
college, then back to a 4-year school (hence the name), without having to sit
out the one year transfer period.  In effect, if these players attend junior
college during the year in the USHL, that counts as their one-year transfer
period, so they are immediately eligible upon enrolling in their new school.