That's not really the case, I think, Tornado. Guys who take a freshman redshirt, get medical redshirts pretty often, if they have a season ender.
The NCAA allows just a 5-year window to complete an athlete's 4 years of eligibility. So he cannot afford to take 2 years of redshirts, or he'll still lose a year of eligibility.
The only exception is a rare waiver of the 5-year rule, that the NCAA occasionally grants on a case-by-case basis.