Before Jan. 1st 2023, Croatia wasn't a member of the Schengen Area and therefore couldn't issue Schengen visas.
On Jan. 1st 2023, Croatia will join the Area and will so switch to issuing Schengen visas on that date
The visa code handbook states :
Bulgaria, Croatia, Cyprus and Romania do not yet implement the Schengen acquis in full. This means that the Visa Code is binding upon them but that until the Schengen acquis is fully implemented these four Member States issue national short-stay visas that are valid only for their own territories.
Will a still valid visa issued by Croatia allow the holder to visit the country?
And/or would it be converted automatically to a full validity Schengen visa, as is hinted by the handbook?