It's not necessarily accurate.
I've called three stores that are showing stock of all 3 models that have been out of stock for a while today.
I did notice that one of store entries changed from 3 greens to 3 reds about an hour after they closed.
yeah they're not cutting off the lines soon enough...which means they continue to sell after the official closing time...so if it updates like you said then it's best to check it just before you leave to go stand in line in the morning.
A guy on Engadget said they told them before opening at the Oakbrook, IL store on Saturday that they were completely out of the 16GB black...despite the website showing them in stock for Saturday on Friday night. Tonight it shows as all in stock once more (after I confirmed over the phone they were indeed out). Needless to say I'm going to be refreshing the status page. Tomorrow I might actually go try to stand in line.
If I strike out there I might make a trip downtown to the Michigan Ave store...since I figure they'll have all the phones there if they don't have them in any other Chicago store. Kinda like the 5th Ave. NY store...it's one of their flagship stores in the States...they wouldn't dare let those run out. Everywhere else, sure....but not the store all the media outlets go to.