Oh I rebooted, I just didn't happen to have the right configuration options to invoke the failure when I rebooted. Not every dev workstation was bluescreening, just the ones with the particular feature enabled.
But as someone already pointed out, the issue was seen on all kinds of windows hosts. Not just the ones running a specific version, specific update etc.
There's "something that requires highly specific conditions managed to slip past QA" and then there's "our update brought down literally everyone using the software". This isn't a matter of bad luck.