Or do Unity already allow any use of the asset (including in other engines), even modifying it and uploading paid to other people if you are not giving any details? In a situation when asset is published already can i add cc0 license in a later update?
Edit:
Also write down what Asset Store is lacking for free, will do it for fun.
If your submission requires a CC0 asset, please provide instructions for users to obtain that on their own. Asset Store will reject content that is CC0, as it conflicts with the Asset Store EULA.
More complex and concrete example:
What if i have an asset that is already published as free but then i also do GitHub with it under unlicense license (or cc0 one).
Then it starts to conflict again and one of them must be removed?
How then community driven unity store assets like super character work? Their second site contains the license that works with EULA so both exist?
Or the super character is old enough snd rules changed on that?
CC0 is not allowed on the Asset Store. If you know of a product that is CC0 and is on the store, please report it. If you have further questions, please create a support ticket.