I don't blame the A's for doing this. It's going to help limit supply and hopefully drive up demand.
At the same time, they can also test whether or not the new limited capacity stadium would actually work. It's somewhat of a test run, if you will.
But as someone who sat in the third deck multiple times (including the walk-off bunt game), it's disappointing to see that option shut off. I'm guilty of the walk-up, day-of ticket purchase as anyone. But that's in part because of the fact that I live in Sacramento, so it wasn't always easy to plan when we could get to a game. Now that supply is limited, I'm probably going to have to purchase some sort of mini-plan and in that way, Wolff and company are already succeeding.
Remember, he needs to see if Oakland can support the team in the new stadium. Since it will probably kill walk-ups you've got to think it's good for the team...but that doesn't necessarily mean it's best for the fans who've been season ticket holders in the third deck for years.