Let me answer your question with a question: did you see a direct statement that I was equating paid witnesses with corruption? If not, you can relax and assume correctly that I was making a statement. Yes, developers will hire "experts" who will speak on what amounts to subjective qualities of a proposal, and by virtue of their assumed expertise, attempt to lend credibility to a building project. This is usually done as a means to undermining city planning documents.
If anything, your confusion with the OMB being like civil court lies at the heart of the problem with the OMB making development decisions. People are not being sworn in to tell the truth as evidence, but paid and sworn in to say something like "as a designer, I think the density of this building is fine and that the city guidelines diminish its aesthetic qualities."