I agree that the temp swing decreases with meat in the smoker and over time as the meat cooks. The first smoke cycle starts with a cold smoker, so it makes sense to me that the temp swing would be larger in the beginning (and especially if the wood catches on fire). With my #2 analog, I typically see a +/- 25-degree swing from the set temp, so at 225, it is not unusual for me to see temps in the range of 200 to 250 degrees.
I have a small temp probe for the box temp on the Thermoworks SMOKE, and I position it above the rack, so it sits a bit higher away from the rack surface.