Obito being confused by the mention of "names"

[Kadmos1]

During the end of ch. 572-early ch. 573 (For those that don't remember, this is the same chapter where Obito had that infamous rain/sweat drop), I'm not understanding the purpose of Naruto saying he won't tell the Bijuu names to Obito.
What purpose would that serve?

I think even if Obito knew the Bijuu's names, that wouldn't make much of a difference to him because he seems to consider the Bijuu to be just tools for him and Edo Madara to use to get the Juubi,

Also, that look he had (that confused look after Naruto told him) that Obito had after Naruto told him this, I can't seem to figure out if this the "Should I be worried about this look?" or a look that's more along the lines of sarcastically saying, "You're telling me this why?".

 

[Bad Touch Yakushi]

Of course it wouldn't make a difference- Obito doesn't want to understand the tailed beasts, just use their power. He's surprised that Naruto said that because he's aware that Naruto has got in contact with the tailed beasts, knows something he doesn't know and has had a major confidence boost.