The timing of a stop and check is something you don't think about until it happens. In my opinion it would be weird to have pulled you over and check on the roadside, I'm glad he didn't do that. Following the group to the next field and checking there was the right thing to do. My buddy was at the boat ramp one time, warden was there, and my buddy asked him to check him right there. The warden refused but checked him later that day out on the water. I suppose if he was missing life jackets or license, can't give a ticket in the parking lot before the boat is floating or a lure is cast.
South Dakota does large operations every year. Game check points on the major highways heading back east. You pull up to a stop sign, they ask if you have any game or fish in the vehicle, if the answer is yes you drive aside and they check your coolers and licenses.