This issue is 100% repeatable, and as far as I know affects all mid-2013 MBAs. When I picked up my MBA from the Apple Store, the tech again said that all diagnostics passed, so, again, there is nothing wrong with my MBA. I proceeded to crash my MBA again in front of him. Then I proceeded to crash his MBA.
In front of the tech, I summarized the simple steps that crash the MBAs in an e-mail, and he agreed that he would pursue the issue with Apple, and keep me informed of the progress. That was about a week ago, and I have not heard back since. I'll follow up later this week.
Apple appears to be in denial on this issue. It may be that they just don't want to admit that the issue exists, as that can impact sales. It just doesn't look good ... "Here is your new MBA, and, by the way, disable sleep if you don't want it to crash."
For a company that claims market superiority based on above-average system stability, failing to even acknowledge that the issue exists is rather disappointing. Bugs, crashes, etc. have to be expected on any computing device ... that's life, and I don't really fault Apple for that. Frequently, the issue is hard to reproduce, and then it is really hard for the company to address it - but they still have to try. In this case, it is completely reproducable, so there is completely no excuse to acknowledge it, and lay out a plan for fixing it. I've debugged many intermittent problems myself, and you really count your blessings when you, or someone else, finds a way to reliably reproduce an issue ... at that point you can assign the fix to a clever intern, and a few days later the problem is behind you. If a company is not interested in addressing reproducable issues, then it is hard to have faith in that company's ability to put effort into the hard-to-reproduce issues - and there are plenty of those.
So, Apple, acknowledge the issue, propose a plan for fixing it, and let all of us move on with our lives.