I agree. They have a threshold for oil usage. Below that, nothing wrong. Above that, they'll do something about it.
Unfortunately you're in that space where the consumption is irritating but not bad enough that they will admit to a problem.
Judging by the lack of response here, either there aren't a lot of members that will admit to owning 6.6's or nobody else has this problem.
I'd say check on one of the GM forums but in my expeience, all they want to do on those sites is blame everything on you and some obscure made-up maintenance task that you failed to perform.
They (the GM forums) will probably tell you that you didn't break in the engine properly.