No, you can't assume bias just because the guy worked for them briefly. He's employed full time as a manager somewhere else, so his income isn't derived from his writing.
I see your point though, but let me ask, will any reviewer who doesn't give a DNA sample and an FBI background check be believable?
If I can put together the money to get a copy of WHFRP I'll try it out and write a review. I have no affiliation with any company or organization in the gaming industry. I'm just a player, and a thorough one at that, so I should pass muster.
My writing skills are reasonable, too.