But you're comparing apples to oranges. You're talking about the inconsistency between monsters. Not inconsistency between PC and NPC rules. Your fly is inconsistent since it does not really follow how other monsters are made. It has nothing whatsoever to do with PC rules.
But, since we're talking about consistency, what is the justification for a 2014 bugbear doing 2d8 points of damage with a longsword? Adding in "Brute" is really needed here? True, they do give it the Brute description. That's true. But, why is a Bugbear a brute, but an ogre isn't? How is that consistent? After all, isn't an ogre bigger and stronger than a bugbear? Statswise it is. So, why does a bugbear with a great club deal 3d6 damage, while an ogre only deals 2d6?
How in the world could you possibly narrate that in a consistent and satisfying way? What have you been doing for these past ten years with this massive inconsistency in the 2014 rules?
Oh, right, you ignored it. Just like you ignored the ten thousand other inconsistencies in 5e.