Not an expert (and I didn't stay at a Holiday in Express last night)
My understanding is you used to get 4 years. You could apply for a hardship exemption for injury, military service, etc. Hardships were basically always granted to extend to a 4 in 5 situation. Some Universities (cough football cough) took advantage by claiming hardships to 'redshirt" freshman – “Dear NCAA he tweaked his hami real bad in preseason workouts and will need a whole year to rehab it honest.”
Eventually the NCAA said screw it when a player hasn't even played everybody gets 4 in 5 that is it, stop bothering us with this stupid stuff.
I don't believe you even need to "apply" for a redshirt it just happens. Academically ineligible skip the full year - 4 in 5. Go on a mission or studies abroad skip the full year - 4 in 5. Need to withdraw from school to take a year off for a family emergency - 4 in 5. Transfer and sit year in residence at the new school - 4 in 5. As long as you miss the entire year 4 in 5, and leave us alone.
Play just 1 game - break a leg, get called up by the military, family emergency etc. etc. Apply for a hardship (“redshirt”) to get the year back. There are rules typically it is less than 25% of the season. But I am fairly certain Spleeman played more than 25% of full year’s games, but the NCAA chose to grant the waver. The NCAA has been trying not to be so punitive to the current players because past programs were so dirty (see SMU football stupidity).
My memory is Ed Caron got a hardship waiver reference his transfer and transfer back. It wasn’t an additional year of playing time but a waiver to the sit out rule. Under the normal rules he would have had to sit 1 full at UNH when he came back. That would have been 3 semesters off the ice. But since he transferred back to the school where he started and his initial transfer was for academic considerations the NCAA waved the additional semester sitting out. (This is an example of the NCAA trying to be more accommodating to the athletes and that 18-24 year olds sometime don’t know what they want)