He will have SP and Util.
Any time a SP is out for a whole season but remain a pitcher, they are manually given SP or RP so they can be used immediately as a pitcher. There has never been a purposeful instance in Ottoneu where a player was a pitcher in the major leagues and could not be used as a pitcher because of eligibility. Meaning, the “waiting 5 starts” scenario has never and will never happen for a major league pitcher.
This will hold true for Ohtani as well as any other SP out for the whole year, i.e. Alcantara (off the top of my head, I’m sure there are others).