Perhaps it's a situation much like investigating Murasaki objects? In order to research ion storms Starfleet vessels, at least some of them, are required to enter the storms. In order to get proper readings the pod must be a certain distance away from large metallic objects (like the ship) or sources of radiation (like the warp drive). Maybe there are actual physical test objects that must be retrieved, similar to the NASA LDEF satellite. Finney had to retrieve the samples and then get the pod back to the ship. Perhaps he had himself beamed back to the ship and was able to hide the evidence of that from the bridge and engineering. He was the records officer and we know he was able to alter the log.