It is still July 29th and PCs will be shipped with 10 on the 29th and people will start receiving the upgrade on the 29th but only a complete idiot would think all 1 billion computers who are eligible for the update would get it on the 29th. The guy writing that blog must fall into that category.
Even when the free upgrade period ends not all of the 1 billion devices will be upgraded. Many people (the vast majority of every day joe pc users) don't care what Windows (MS) has to say about upgrades or updates even when they are free of charge. The only thing people are eager to install are maleware which promise them a "clean" Windows and getting certain photos. Many of these users see their PC like any other household applience. Have you ever updated the firmware of your washingmachine? So why update the OS of your PC? The only ones who are upgrading on July 29th are the insiders and a small group of people who didn't know that there was an insider programm. Every other user didn't even know there is a new Window to upgrade to free of charge. Then only the bought newly PC or notebooks are haveing Windows 10 installed. The promise of getting Windows 10 on 1 billion existing device plus the new devices is for developers not to overlook the plattform as a whole.