According to the author's bio [1], he was remastering photos of Neil Armstrong in 2019 for NASA for the 50th anniversary of Apollo 11 so clearly the timing lines up. Multiple sources on NASA and elsewhere point to that Flikr gallery.
> The quality of the few I sampled is also nothing special.
The ones in the TFA are remastered - color correct among other things. The ones in the Flikr are the unprocessed versions of Apollo Hasselblad photography scanned by NASA's Johnson Space Center. You can download the original 4000x4000+ resolution scans from Flikr.
From that site: "The raw output from the digital scan of a 70mm Hasselblad frame, is a huge 1.3GB, 16-bit TIFF file. At approximately 11,000 pixels square, a single image would require a 12-foot x 12-foot computer monitor to display the whole image at standard resolution. "
The Flikr images must be jpg conversions of the original TIFFs, certainly in an attempt to reduce file sizes. I'm not sure where the 11,000 comes from. The JPGs are 4400x4600. Perhaps the original TIFFs were 11,000x11,000 pix.
In the US, government organizations are not allowed to copyright their work. They can, however, obtain works that were copyrighted by someone else. But pretty much everything coming out of NASA is public domain, though they don't put a lot of effort into publicising that fact.