OK, you're right: there SHOULD have been smiley by that post, because I was certainly kidding when I said "jiveass." I'm not knocking the quality of their product.
However, aesthetics are more important to some of us than others. The thought of a label corralling together an artists' rare releases and NOT including the original cover art comes off as incomplete to me. It would only make me want to find the original albums that much more.
And I simply find Oscar Peterson an odd choice for Mosaic, compared to others they've reissued, simply because there's a huge rack of OP albums in every jazz record store. That's all.
On the bright side, I don't buy these things, so be grateful that you have less competition. I won't buy, though, as long as they don't include the cover art.