I think you are missing the point they were trying to make.
If NASA was having visible issues and difficulty in trying to get something like Hubble working in space, then perhaps the US’s spy agencies (known or not) also had the same difficulties. NASA employees wouldn’t need to have known about the NRO to help provide cover for their capabilities. Just publicly showing their struggle - for transparency - would have been enough.
(If NASA had a clue about the NRO capabilities or not, I doubt they would have cared. They still got their space telescope!)
It's more, "Hey, if NASA is having trouble with this, with their big brains and frontier research, no way military capabilities exceed theirs at any real capacity." It's one thing to say they're a few years ahead, it's another thing to say that the military was working on a Hubble when the people who would eventually work on THE Hubble were still in grade school.
It makes me wonder about things like AR/VR, where, likewise, things are just starting to hit the lit sphere, with great difficulty; does the military already have tech that's 3 or 4 generations ahead?
It's not a question of "If", the Hubble mirror was made by Perkin-Elmer which had a long history with the NRO. Meaning that the TS or TS/SCI level program-cleared executive leadership at NRO's contractor knew exactly what was going on in both worlds.
https://www.google.com/search?client=firefox-b-d&q=perkin-el...
Whether any of that information would be allowed to go in the reverse direction back to NASA is another question entirely...