I've also talked to a person who was in the Pentagon when some disks went "missing" from a room because it had poor locks on it. He had tried to tell someone that they were the wrong locks for the security level of the room but was told "that's not your business".

Kissinger became aware during the SALT negotiations of how much the Soviets were misinformed about US nuclear capabilities, and that they tended to overestimate. That imbalance helped him negotiate those treaties. One can assume the State Dept. would want to keep that advantage if they could. The USSR was also concerned about how they would defend themselves against a Western attack. If they weren't they wouldn't be making these treaties. Everyone assumed that if war broke out both sides would be wiped out. The point of the arms race wasn't to win in a war, it was to see who would fold first.

Don't forget that "SDI" was an umbrella. If you had some project and could slap that tag on it you were guaranteed a substantial contract for it. That you could get away with promising an arbitrary delivery date made it that much more of a cash cow. And the Pentagon was fine with that since it would never need to be finished. It only had to look convincing.