BTW, when I checked copyright I first searched on Worldcat. The first edition reported by Worldcat (at least based on the search keys that I used) was a Schirmer edition dated 1925. At that point in time I suspected that the claimant was Schirmer, based on an "Editio Princeps" term still valid in the US. I was going to check whether a valid copyright registration was made in 1925 and renewed in 1953, but then I found that a 1881 edition was mentioned on IMSLP, which makes "Editio Princeps" clearly not applicable.
The copyright clarification text may be something like:
This performance is based on CPDL edition #03073, which can be freely performed and recorded. The work itself is public domain all over the world, as it is a SATB arrangement by Tchaikovsky (died in 1893) of the original work by Bortniansky (died in 1825). The SATB arrangement was certainly published in 1881 as an item of the collection "Choral complete sacred works by Dmytro Bortniansky". These elements make this work ineligible for copyright, including "Editio princeps" provisions, in the US as well as in any other countries.