Good luck finding one without it lol. Sometimes youll see wild spp. with dorsal occeli but 90%+ of wild caught & captive oscars are going to have a tail oceli.
yeah it tends to be more prominent in the wild Os and some wild ones will even have ocells on their backs like stated but most captive bred ones will have one though the more inbred they are the less prominent their occels become until some lose them altogether but most still have them