You are correct! But this is the situation with our entire adversarial legal system. We have in general not solved this by excluding expert witnesses, so it is

You are correct! But this is the situation with our entire adversarial legal system. We have in general not solved this by excluding expert witnesses, so it is indeed out of the ordinary to block testimony like this. For example, police have a long-documented history of not giving reliable testimony. And yet these "experts" provide testimony at most criminal trials. If a state is willing to allow its police to provide expert testimony, why not its other employees?