An application bug that causes an operating system crash isn't minor. What this demonstrates is that it is possible to use Siri to crash the system. That's actually a serious security flaw that may be exploitable because it demonstrates that there is a problem with application sandboxing. Furthermore, given the close relationship between Apple's various operating systems, it may be a flaw that's exploitable elsewhere.
So, while you may think people are overreacting and that having your watch crash if you say the wrong thing at the wrong time is fine, hopefully Apple are taking it rather more seriously because you can be sure that there are people "out there" that are already looking into what happened and how it could potentially be exploited.
As annoying as it was, something to bear in mind here is that this wasn't a generic Siri issue as my iPhone was able to handle the request just fine yesterday, whereas the Watch didn't.
In addition, given everything Siri does, it has a deeper integration with the OS - and, last I checked, didn't run in the same Sandbox context that Apple request 'normal' applications to run in.
Yes, this was annoying, but it's equally going to be related to something stupid as a negative one overflowing into an unsigned int causing a bad bit of memory somewhere, just because some idiot didn't check for the Daylight Saving shift somewhere. Either that or the array that brings weather back for the next 24 hours didn't expect to have two 1AMs - something daft like that.
It's annoying, bugs happen and I can pretty much guarantee this'll be fixed by Apple, even though it's over for the next 6 months - or even year (depending on if it effects both the spring and fall changes, or juts the fall ones).
Panicking that this is a serious compromise is, to be honest, sounding a little chicken-littleish.