Pointing out body parts yet?

Hi there I'm new here and I haven't posted much yet but anyway I'm just a little paranoid and seeking advice or reasurrance that my toddler is not the only only. Anyways my son is 15 month and he was born 9 weeks early so his adjusted age would be 13 months and developmentally we always see him as 2month behind his actual age. I have been working with him for a month now on body parts and tried all different strategies and he is not interested I'm now trying to just focus on one body part at a time and this week I'm working on belly and nothing he just isn't interestred he waves ,highfives, claps ,and says dada and kitty cat with meaning. I know it might still be early and I'm guilty of comparing and recently spent time with a younger baby who knows three body parts and it kinda through me for a loop. I just hope I'm not failing at teaching him and he is just not inerested in that yet.