If it was just a science thing or they didn't care about the security risk, I don't see why they'd keep forming new organizations that are increasingly secretive.
Because it's not just a science thing. It's a potential threat. Threat is defined as capability x intent. We are seeing these things with insane capabilities, but not really any intent (other than maybe observing our technology).
They already responded to FOIA requests, briefed Congress publicly and privately, and announced AARO when they didn't have to. We're pretty well-informed, and Congress has some oversight. It's very ordinary.
The former Deputy Secretary of Defense for Intelligence wrote a blog alleging that there are black projects hidden within DoD contractors that are reverse engineering non-human intelligence craft. He's presented enough evidence to congress for them to add specific legislation to bring these programs to light.