The NLI is a designed to halt the recruiting process. That's why it exists. To give recruits a break, that have decided where they want to go. All institutions that participate with program agree not to pursue an athlete that's signed a letter, and it's all entirely voluntary - by all involved. No school is required to issue NLI's and no recruit is required to sign one.
As of now, It's a committment to the educational institutiton by a student athlete for a year. It's also a commitment by the Institution to provide financial aid of some form. That's key. The two things go hand in hand. The financial aid paperwork is separate from the actual NLI, but it is integral to the process. You can't have an NLI without financial aid. You can have financial aid offered and agreed upon, without an NLI - but the recruitment by other schools won't stop.
If a student athlete does not desire, or need financial aid, there is absolutely no reason to sign an NL, except to stop the recruiting process formally.
The choice to either accept or defer financial aid, can be made later, but the committment to provide financial aid, from the university - MUST still be part of the process. There is also no standard in the language as to what financial aid provisions are agreed upon. (i.e. partial scholarships exist in addition to full scholarships in intercollegiate athletics)
THe questions posed, (2 of them) were about whether or not an athlete needs to sign an NLI to get financial aid I believe, I don't remember the exact quesitons. THe answer is no, and there is no necessary reason for a player OR school to sign an NLI. And there's nothing either preventing or requiring an athlete to sign an NLI. It's all completely voluntary.
An NLI that is not signed by both parties is VOID after 14 days after it's been formally issued. A signed NLI by both parties has 21 days to get into the conference offices from the date of final signature, or it's void. Any student under age 21, needs to have the signature of a parent orlegal guardian in addition to their own for it to be valid.
It's very rare, to have an NLI be issued, by a university, in accordance with all the rules and regulations - and then have the student athlete, sign it and then choose to opt out of the agreement. There are provisions that exist, for students to appeal and have the terms and conditions of an NLI waived after they've signed it. To my knowledge, it's also rare, to get the stage of the process where an NLI is formally extended by a university, and it is not signed by the recruit.
As for walk ons, and who qualifies as an actual recruit, and who doesn't, and what makes a recruit, a recruit officially and what doesn't, etc. etc., there are well over 400 pages of NCAA rules and regulations that don't do a real good job of defining what is what.
Check and verify if you want.
