It's just part of the process and almost every trial. Both sides move to admit some evidence and keep out other evidence. All outside of the hearing of the finders of fact. The article probably oversimplified and misinterpreted the argument. Experts provide context and they provide learned opinions, but it is still just an opinion based upon the facts as presented to them. They are not eye witnesses. To not make the limiting argument could be malpractice. Even a weak argument forces the other side to proffer evidence as to why the testimony should be admitted, providing additional insight to your opponent's case. Also, this motion to suppress may be designed to narrow the expert testimony to topics in which they are actually an expert.
For example: A pilot expert may testify about procedures, training, actual operation of the aircraft. But if he testifies, what he would have done under the same conditions, that is not expert testimony, that is merely his opinion as a reasonable pilot. If he testifies as to whether the defendant acted reasonably under the facts at issue, that is usually an acceptable expert opinion. Now the other side can easily find their own expert who comes to the opposite conclusion. complex cases typically do become a "battle of the experts". Additionally, it's less expensive and more efficient to get these arguments out of the way before the jury is empaneled and, there are some objections that if you don't raise at certain stages of litigation, you waive. They may not be raised later during trial, or on appeal. Hope this helps.