Something like that is an indication to look at things more closely, but isn't really undeniable proof for anything.
For example, the Dadao has slightly less damage against armor by only a few points for longer reach and greater speed compared to the bec. Many other 2h have sizable tradeoffs against it, too. You are overestimating the damage advantage of the bec. Bonus damage to the head is a bit of a mystery. It boosted my 1h damage by above 60% when I tried testing damage with the reporter, so I'm not certain if it's different for pierce attacks. Overheads deal bonus damage no matter the hit location. A bec/awlpike also receives the same speed bonus boost as any other weapon.
What I am trying to say is that there are many damage multipliers that can be at play all at once.
