No idea, beyond that iirc, the available information was released previously or release is currently not possible.
I don't know the regs for records retention, particularly of paper records. It's also possibly that any "file" was microfilmed or scanned in an early process that now is unrecoverable.
OT for Park Service, but spot on for records storage: The Federal census is to be released to the public 73 years after the year it is enumerated. The 1950 was released this year.
There is a problem with the 1960 census, scheduled for release in 2033. The data was stored on large magnetic tapes, about the diameter of a record album. At the time, this was an excellent storage medium. When I was an undergrad in the late '70's/early '80's these machines were in use by the university & many levels of government for program storage & records storage.
Fast forward to today -- the machines are no longer manufactured. Replacemtn parts are not available. Computer techs are not trained to maintain them -- most have never seen one. The OMB/Bureau of the Census has no way to read the magnetic tapes, now way to release the Census.
If Yosemite's 1981 files are on mag tape -- they may be released after OMB solves that census problem?
I have completed extensive genealogy over decades. I have files in at least 3 unreadable formats in a safe deposit box. Safe, all right! Anyone have a SyQuest drive that works? Lost mine in a lightening storm in the 90's.
jmho ymmv lrr