They were previously available to the public, but only on premises, so they might contain previously unknown information regarding the spy satellite programs.
The Backfire (Tu-22M) controversy was typical of many cases where the USAF intelligence branch over-estimated the range of Soviet aircraft. They assumed that Soviet airframes and engines were similar to contemporary Western ones. Actually, the airframes were heavier because of higher load safety margins, and the engines were gas-guzzlers due to inferior metallurgy in the turbine blades. Neither of these issues could be addressed by overhead imagery, so it is not surprising that there is little about Backfire in PHOTINT documents.
Off topic, what was the R-7 configuration controversy? Just a little curious.
It's interesting to see how much they knew about Soviet rockets in the 1960s, and how much of that knowledge came from satellite reconnaissance, compared with use of human resources. The reports generally are clear when information comes from analysis of imagery, and not clear when information is presented unsourced, as in "we think that the booster that uses Pad 12 is the same as the booster that we know uses Pad 36 because the supporting buildings are similar in appearance" as opposed to "the booster at Pad 12 has a thrust of 134,000 lbs".
These Project Hazel studies are characteristic of most Convair projects from this era: optimistic to the point of absurdity. Just compare them with real Mach 3.0 aircraft like X-7, BOMARC, Navaho, B-70, and A-11/SR-71. The long ranges are grossly inconsistent with the small fuel volumes. I especially like the inflated fiberglass wings for stealth!
Just imagine what the CIA thought after seeing the pics of the Ecranoplan?