I guess that different Hive Fleets have different Hive Minds, each with it's own unique "personality". One Hive Fleet adapts, the other with seer numbers, and yet another tries to go in a two prong attack. The way each Hive Fleet fights and how much resources spent on X and Y are depending on the "personalities". These personalities aren't true personalities just minor quirks that seem to of shown up due to w/e variations they have. That's what I believe. Is it Canon? Who knows. Does it make sense? A bit.