China Koi Fish 2017 - What About Them ?

Allegedly China intended to issue a mini-sheet of Koi fish in 2017. According to a seller, these were never issued with the following justification:

"Koi is Japan fish, not China fish, so cancel issue, it is specimen only, have gum, can not use for post".

Assuming "Specimen" in this case means not issued.

Problem is that these stamps are not registered in Michel in 2017. In Michel, if unissued, they should get a Roman numbering, but again, not to be found.

Anyone can provide any insights on this ?

Thank you
Dieter

Checked with a Chinese stamp study group

The mini-sheet is a postally non-valid private print. Such "souvenir sheets" seem to be not unknown from China