If a review is 100% unbiased, it's not a review, it's simply a recitation of facts. A review is explicitly the expression of opinions, hopefully well-informed from experience and knowledge. A good review is one in which the reviewer's biases are made clear and used to discuss the subject in question.If a review isn't 100% unbiased, it is worthless, and not actually a review at all.
It's true that if BTW has been giving Thomann products favorable reviews in a lead-up to this, that might be a bad look. But, on the other hand, is BTW known for providing negative reviews of anything?