It is not that simple. Hubble was developed in the open by nasa civil servants who did not have access to KH-11 design. The non-optical systems are entirely different between the two platforms. Some of the contractors were shared however, and may or may not have reused IP and tooling. A lot of it is convergent evolution though. The size of the space shuttle payload bay was set by the DOD to be large enough to carry or return a KH 11 spy satellite, even though it was never used for that purpose AFAIK. The size of the Hubble was obviously the max size they could fit in the space shuttle. So they both ended up being identically sized optical telescopes, and it’s not surprising that similar design requirements end up making similar devices.
My grandfather worked on some aspect of the Hubble design (I was young; I think the timing would have put him at Lockheed M&S in Sunnyvale at that time). He never said anything about his work on it being classified. He used to say "when I retired, the stack of NDAs was this tall" and show his index finger and thumb being about 3 inches apart.
He was a very serious guy and would never talk about anything he shouldn't have. So yes, I believe the fact that he was willing to talk about Hubble meant it was done in the open. And also, he never expressed any sort of amazement that it was still up there, working. Why wouldn't it be?
Hubble was done in the open, this is an established fact. Since some of the contractors companies were the same, though usually not the same employees, it’s an open question we plebs may never know as to whether some aspects of KH-11 were declassified and shared with the workers doing Hubble.
But if we’re talking anecdotes, I worked at Lockheed as well, though not back then, and one of the stories I heard was that when the Hubble was in Sunnyvale to get tested in the vacuum chamber, one of the KH-11 workers stopped by to check it out. He spotted something that was a unique invention for the KH spy satellites and alerted the government. It took a LOT of paperwork to show that nope, it was just accidental convergent design. It was a tricky thing to sort out, but really the only way of solving that problem given the identical requirements.
> usually not the same employees, it’s an open question we plebs may never know
The impression was that my grandfather did classified work more often than not; he probably would have been one of the crossovers if it had been the case. He was exceptionally severe if any discussion came too close to whatever line existed, not that anyone else knew if or where such a line was. My mother and her siblings did not find it to be a very happy childhood, on the subject of anecdotes :). The stuff he talked about was fascinating, but you learned quickly not to ask many questions.
We don't know how much of it is the same but the mirror is very similar.
> KH-11s are believed to resemble the Hubble Space Telescope in size and shape, as they were shipped in similar containers. Their length is believed to be 19.5 meters, with a diameter of up to 3 meters (120 in).[5][23] A NASA history of the Hubble,[24] in discussing the reasons for switching from a 3-meter main mirror to a 2.4-meter (94 in) design, states: "In addition, changing to a 2.4-meter mirror would lessen fabrication costs by using manufacturing technologies developed for military spy satellites".
> In January 2011, NRO donated to NASA two space Optical Telescope Assemblies with 2.4 meters (94 in) diameter primary mirrors,[53][54][55][56] similar in size to the Hubble Space Telescope, yet with steerable secondary mirrors and shorter focal length (resulting in a wider field of view). These were initially believed to be KH-11 series "extra hardware", but were later attributed to the cancelled Future Imaging Architecture program.[57] The mirrors are to be used by NASA as the primary and spare for the Roman Space Telescope.
And the shuttle was designed to launch and recover DoD payloads. There's a lot of "military synergy" in the early space program. No one else was interested in paying.