Well, in my days I read "is optimized for Mozilla 1024x603" as "I am not savvy enough to make IE align my stuff correctly but I am an armchair open standard freedom fighter condescending enough to stick my W3C-validate logo in the face".
To be honest, we were frustrated that it slipped through. As in exactly as you say: it's sloppy and should've really not let this happen. Completely our fault.
I can see how you would naively assume that it's something to do with some CSS issue, but it's nothing to do with CSS. We're trying to use a brand new technology for the first time using libraries that have just been written, and newsflash not all browsers behave the same way.
The browser block is up while we figure out where the cracks are during _this prototype_.
>The UJO MUSIC Prototype is optimized for Chrome on the Desktop.
People says that Safari is the new IE, but I have come across too many Chrome-only sites to think otherwise.