Indeed on first read, I'd say that he presents a convincing argument. I'll go along with his diagnosis that there's no hole that could open you up to arbitrary code execution. If that's your definition of a security hole, then it follows that there's no security hole there. But it's still leaving you open the possibility that the operating system may crash for no apparent reason, causing you to lose any unsaved work.
Lost work... Depending on how productive you are, that can easily result in monetary damage being done.
As I posted previously, that leaves you in no worse a situation than you always are if you're running a desktop computer without a UPS. But I think that it still warrants attention.
At best it still qualifies as an inconvenience, because the savvy user who saves her work regularly will only have lost 5 or 6 minutes of productivity including the reboot. At worst, it can result in hours of lost work for the user who doesn't understand the "save your work" mantra -- especially if we're talking about somebody who's protected by a battery backup and doesn't think that unexpected reboots should be possible on such an inherently stable operating system.
And it's undoubtedly a bug inside Apple's software that's causing this problem, therefore it is absolutely appropriate that Apple should be expected to fix it. I appreciate anybody's effort to bring such bugs to light, because that increases the probability that Apple will find out about it and fix it.