It's normal, they manufactured these machines weeks ago, and they probably found some bugs since then. I guess they're only releasing the updates now to avoid rumor sites going "Apple issues firmware update for unreleased notebook, therefore Retina MBP confirmed!".
I totally agree. The updates have been around, ready for installation for a while now, they just simply won't open every box and update an already packed MacBook Pro to update before they get to the consumer. (Obviously)
I assume the software updates were available the moment a new owner setup a new MacBook Pro.
Remember buying a new Mac in the past and it only had 10.X.X installed, and you could update it to 10.X.X+2? immediately? This is no different. Although I would guess they already all had 10.7.4 installed and that's probably the minimum OS. They likely will never release a OS X 10.7.5 anyway. If they do, it may be the only other time it get's released after the next major update, remember 10.4.11, it came right after 10.5? Then again, that was a $129 upgrade, today it's only $19.99, so the only reason for 10.7.5 after 10.8 release would be for the original Core 2 Duos that run Lion today but can't run Mountain Lion because of their 32-bit EFI. (I know that's not the main technical reason, but it fits.)
10.7.4 would be the lowest interim update before the next major release since 10.0.4 on June 22, 2001 (11 years ago!). It does appear that we'll see new major updates every year now.
OS X 10.9 in 2013, 10.10 in 2014, 10.11 in 2015, etc. (When do you see it ending? The end of OS X in 2020 with OS X 10.16? I guess it would be when the keyboard and mouse/trackpad are obsolete.)
