Most Valuable Warrior in Co-op

[Lucent Beam]

I tried to get MWV in co-op last night, and while Tadakatsu Honda got the 1000 icon, the cutscene never came up and the achievement never popped up.

It was my save file. I was player 1 as my lord Nagamasa Azai. My boyfriend was player 2 as Tadakatsu Honda.

I'm wondering why it didn't pop up and I'm thinking either:
-Player 1 has to get it to get the achievement.
or
-Your lord cannot be present in the battle at all.

Anybody know which of these it is? I ended up getting the achievement myself using Mitsuhide, but when we go through and get the achievements for my boyfriend, I want to know if we can do it co-op.