"There are zero guarantees at any school."
There are schools out there that guarantee 4 years.
Starting in 2013 NCAA allowed schools to offer multi year scholarships. You sign your NLI and along with that comes a financial agreement that outlines amounts for years 2,3,4 & 5 if needed. The NLI is for one year. If the coach decides to cut you after the first year, he can and will. The financial part of the agreement still stands until you leave the school or the timeframe ends.
Very few, if any stay. Most move on to the next school where they are wanted and have a better chance of playing.
Not sure what you mean when you state that the NLI is for one year. The coach can (and do) cut NLI signees in year one. Have watched this firsthand with freshmen this fall being cut.
Because they signed their NLI, they are "required" to attend the institution for one academic year as a full time student. If they do not fulfill this, and they enroll in another institution participating in the NLI program, they are required to complete one full academic year at that institution before being eligible to compete in intercollegiate athletics. This can be appealed, but without appeal and favorable ruling, the student athlete must sit out.
So to that point, the school is under NO obligation to not cut the player in year one.
As for the financial agreement, the school IS obligated to meet the terms provided the student remains in good standing. As you mention, most want to play and will leave, freeing the institution of the financial agreement at that time.
All the NLI really does is ban any active recruitment of the athlete from other schools and lock the student athlete into penalties should they transfer to another school. Nothing in the NLI guarantees that the team retain a player in year one.