You have explained the secrecy—however the notion that higher ups at NASA ignore UFOs strains credibility—it is much more likely they have a compartmentalized sub-group that deals with it.
The SOP also prevents release of UFO material to the public.
I have been in meetings in NASA facilities. If you mention UFOs in a meeting, you don't get an invitation to attend the next one. The only astronauts who talked about UFOs are always the ones who already know they have taken their last ride.
NASA does censor material they release to the public. They do that at the beck and call of the military and intelligence community. Internally, they desire to ignore all of this so that they can go about their missions without attracting off mission attention. They will turn cameras to avoid "fun stuff", not out of censorship but merely trying to stay out of this issue. If they are studying UFOs, it will be going on in non-public projects. Do they have non-public projects? I don't think so. My late brother was a department head in Lockheed on the Shuttle program. He told me that people knew about UFOs and even talked about them in bull sessions just like anywhere else. He did not know of any official channels to handle that stuff; but, that could simple be because it was not within his need to know. He did converse with astronauts who told him for sure they had seen "things".
My brother was eventually "spun out" to Space Services, Inc, which is a Lockheed subsidiary. Deke Slayton was the president of that company; and, my brother worked quite closely with him. Slayon told my brother about UFO encounters he had dating all the way back to 1951 and up to his last flight. This subject was never a topic of official meetings.