three different types of haki
his forte was one specifically , armament
getting conquerors haki you could argue there is a build up to it given his dream
him using the advanced version of it 20 mins after tho is fucking convenient.
its not a moot argument
top fighters tend to have conquerors
so if oda decides certain fighters need it to get to the top and wants them to use it within 20 mins as well, I really cant complain . who knows what plan oda has for tony chopper