IMO, if the research is in an area that he is interested in then its a good thing. I would not necessarily expect that he would gain instant access to a prof simply by joining in. However, if he makes strong contributions to the project he will see his visibility and access grow. My S joined a research group in his sophomore year too. He started off by contributing in some easier low-visibility tasks, but he was able to rapidly grow his responsibilities and visibility by his commitment to the project and his ability to actually contribute at a grad-level.