What is your point? We don’t know what they took. I suspect some would be grooming items that only he used.
Actually we don't know if they took anything, or why. And even if the FBI says they did something it may well be a untrue. Look at all the testimony related to the Russia investigation where FBI employees at all levels up to the director seemed to have trouble telling the truth.
They probably just went over to the house to get some footage on the evening news after they saw Dog the Bounty Hunter got some attention doing the same thing. The jackets with the big "FBI" logo on the back seem more for the cameras than anything else.
They and everyone else working on that investigation would have to be idiots not to have obtained a DNA sample they could associate with Brian Laundrie some time ago.