The NFA isn't going to deny your trust. They aren't lawyers. However, if you ever have a legal tangle, the court just might invalidate your trust.
Every state has slightly different laws. Lawyers charge the money they do because they have a specialty occupation and specialty knowledge that we don't. It's why we pay them and doctors big bucks. You can always represent yourself in court or use a free public defender, but I think we tend to know how that goes versus paid legal representation.
I'll let you in on my experience. When I got my first can, I got a free complimentary trust by the shop I went through, which was about 10 pages of legal mumbo jumbo. I filled it out and submitted my Form 4 on trust. I got an approval four months later and I was happy. I ended up buying another can down the road and decided to pay a lawyer to restate the first trust it because I wanted more out of my trust, such as designating trustees, beneficiaries, and doing asset distribution upon my passing or incapacitation.
Guess what?
My lawyer went over my existing trust and pointed out several areas that made my trust invalid by law and worthless. How was I supposed to know that? I don't have the legal expertise to determine such things. I ended up restating the entire trust and expanding on it to cover all my legal grounds, specific to the state in which I reside. Best money I ever spent for peace of mind from an estate and planning lawyer that is also an NFA fan. There are probably thousands, if not tens of thousands of people out there with the same or similar free trust setups that were approved by the NFA but technically a legally invalid trust. You aren't going to know if the trust is any good until it gets put to legal scrutiny.