I think the impetus to put structure and funding to this from the NDAA is the rapidly increasing development and use of drones, hypersonic missiles, and stealth craft by world powers. If we can't easily identify what they are, then trying to figure what they are is pivotal because without doing so just muddies the intelligence waters. The US has already determined these things are violating restricted airspace, so it would be logical for them to get a better handle on what these things may be - whether foreign adversary or something else.
There are "Five Observables" of UAP behavior (as defined by former Pentagon official Lue Elizondo):
- Anti-gravity lift
- Instantaneous acceleration
- Hypersonic velocities (with no signatures, like sonic booms or contrails)
- Low observability/cloaking
- Transmedium travel (can move between water, air, and space)
A bit more on these from a Washington Post article earlier this year with Elizondo:
UFOs & National Security with Luis Elizondo, Former Director, Advanced Aerospace Threat Identification Program
Former AATIP Director Luis Elizondo explains the observables associated with UAPs, and says current observation technology has record them underwater. “There’s five distinct observables that set this technology as I mentioned earlier aside from everything we have in our inventory. The first is hyper sonic velocity, the ability to change directions instantly… the third observable is a bit like ‘cloaking,’ we call it low observability, but the forth observable is… trans-medium travel… the ability for an object to not only fly in our atmosphere–low and high altitudes¬–but also potentially in a vacuum environment like space and even underwater… We’ve seen these things, they’ve been recorded not only in our atmosphere, but there’s data to suggest that they’ve also been tracked by some of our capabilities underwater as well.”
I mean, it's not illogical to want to gain some scientific insight into what pilots are observing on a now almost regular basis.