Yeah, the dilemma is real. Retesting with new bios updates sets a terrible precedent. For one, you'd have to continually update all motherboard reviews as new Bios versions appear. That'd be an extremely valuable service, but it'd also be insanely time intensive and beyond TH's scope. It'd also remove pressure from the manufacturers to get it right the first time.
I like Bios updates. They fix bugs, improve compatibility with new releases, etc. But how hard is it to get the basics correct the first time? Bios updates that improve performance should be rare, blue moon types of updates. Calling 500mv vdroop a 'bug' is making me question their QA process.
At the same time, if I'm looking to buy a mobo, I'm not really going to take into account the old bios. I want the best overclocking ability. I'm not sacrificing that to make a statement about proper QA before release. So the part of this review that matters to my purchasing decision is the Post-Game show. Except that I know that the comparison boards might also have updates that haven't been tested making the comparison kind of useless.
So, I end up mostly ignoring OC results in these kind of reviews unless they are anomalous. Instead, I head over to somewhere like overclock.net's forums and make use of the data sets in one of the cpu clubs (usually a few months after launch).