Black Pirate

I don't understand why it can't... doesn't make sense to me

Because the actual active skill's name is different. Not only the effect needs to be the same, but the skills's name has to be as well. Batman's skill is called Intimidation, whereas this is called Virtuous Foundation.

Because they might not want different sets of creatures to be subject to the same changes. There are actually quite a few creatures in the game with identical skill effects as other creatures, but different names.

Since you have posted this, they upgraded Virtuous Foundation with Okuninushi's uvo, but they have left Intimidation untouched. This attacker D/D Batman is the "weak" and "common" Batman compared to the rarer D/L and D/W Batmans.

He's supposed to be skillup fodder for Okuninushi or he can serve as a makeshift Dark delay if you're really desperate.

use them for skill ups for other monsters

after it's been more than two years I will help you out. He is a great S- rank sub that with 2 stars and a delay and boost if needed is good. S-rank dungeons will never run out so it will be good to hold on to this guy. By S-rank there are different varieties of it such as Rushes that are 50k collab are 150 I believe and regular Skill dungeons such as Echidna are 200k.
There is an S- rank calculator here. with him being a 2 star sub you can use a 6 star leader and friend. this guy and 1 star subs and will get over 220k on rarity alone. Use this guy and regular high star monsters and you are sure to get over 50 k. Use this guy and another 2 star and regular monsters and you will most likely get 150k.

Other uses for him would be if one day you roll Okuninushi. My suggestion is that is a good idea to keep at least one of this guy or other potential low rarity S-rank monsters.
February 8 2016