Please see Paizo for the proper way to do an open playtest.
To be fair, that summary was probably written with the idea that the Open Playtest would be out at the time (perhaps right after PAX East, which could still happen). The summary could be wrong, but if so is likely because they are receiving really valuable feedback through their current playtest mechanics, in turn driving them to make changes before the larger playtest begins.
I'm on an NDA, so I can't share what I would love to share about the playtest methodology (and I probably will never be able to do so, since their playtest methods are unlikely to ever be public knowledge). But, I don't recommend jumping to the conclusion that the methodology is lacking compared to Paizo's or any other RPG company's playtest.
Keep in mind several things: A) There are non-public components to the playtest that are important. B) They received very good feedback from the NDA but open to anyone playtest at DDXP. C) They are working on a scale that is substantially different than that of other companies and with far bigger goals. D) Even when Wizards' open non-NDA playtest initiates, it will not be a 1:1 match of what Paizo or any other company has done previously.
I'm a big fan of playtesting. I like various aspects of what Paizo did, and I like what has been done by other companies (I have and do playtest for several companies). Playtest approaches should vary based on the product, the goals, the audience, and many other factors. This makes it very difficult to say one approach is superior to another. To really do so you have to know a lot about the inner workings of an RPG company - as well as of other companies so you can run a comparison.
My advice: enjoy all the games you can and enjoy the diversity amongst RPG companies. If you have the means to go to PAX East, do so. It will be a fantastic opportunity to be part of the process that shapes D&D (and which will likely influence all RPG companies in the future).