you are giving too much credit to garp, love him to death but the dude is a simple minded fool. casually insults celestials and kings and goes "oh wait i cant do that, forget i said anything"
being a pirate and a rev is a bad thing, particularly in garps eyes. he wanted dragon, sabo, ace and luffy to be marines, not pirates and revs.
i think dragon like coby to garp. as mention garp probably lied, as garp had overshadow expression. oda does this overshadow expression when something bad is done/or said for the character reaction.
honestly there no reason to hide kuma eye pre time skip, only to reveal in the timeframe luffy need to be born, kuma who matches luffy in genetic looks etc.
when look at dragon, imo he prob someone trained like coby under garp teaching.
there is no genetic looks between dragon and garp or luffy.
luffy has kuma eye and nose, and hair, that not drawing mistake. i don't know full story because oda not revealing it.
he hid god vally, and what did garp say his number 1 rule was?
save the babies first.
meaning garp did meat kuma, ginny, ivankov- who are children. to get saturn of kuma who imo could not defeat saturn in god vally. even the kids mention garp after going back to kuma hometown.
so oda hiding something important.
also garp is caught by blackbeard.. so kuma will reunite with him later for maybe more god vally lore.. if kuma and bonney continue travelling with luffy, as vega punk request for luffy to protect bonney, which include kuma.