I wonder how the USDA can demand anything regarding images created well before the copyright cutoff of 1929. I strongly suspect that's boilerplate text with no actual force.
Oh definitely no force behind it, but just annoying to see. These kinds of issues don't exactly block usage, but can plant a lot of confusion or hesitation for potential users.
I wish agencies proactively embraced "please go use this awesome stuff" mentality vs gatekeeping by default.