He is feeling more sore than usual because likely the weight was too heavy for him, and he was not able to control the descent of the weights properly, leading him to overexert himself in the exercise. He may want to rest a bit longer before returning to workout as normal, as he does not want to injure himself in the long run. In the process of not performing the seated leg press as he should (in a safe manner), he risks overusing his muscles, and maybe even tearing a muscle or ligament in the long run.