You are correct, a smaller smokers should be able to keep a more uniform internal temperature. Loading it with just three chubs also helps a lot.
Overloading a smoker with more product than the smoker has the heating capacity to manage can give uneven results.

processhead - yes… I used an external grate temperature probe as well as a meat probe. It’s a good quality unit from Thermoworks that I trust. I use a small smoker from Cookshack (SM009-2). The cooking grates are small - only 12" X 12" or so. I had 3 10" long chubbs on the center grate with the temp probe placed in the center of that grate (right in between the chubbs). I don’t see how in an area that small that there could be some spots significantly hotter than others - but who knows.

At any rate, it all turned out well. I was just curious about the small amount of fat out that I saw when I know that the overall high temp in the box never exceeded 180.

It’s a good idea to check your smoker chamber thermometer /temp probe periodically with a known to be accurate remote reading thermometer. Your smoke schedule is only as good as your data and an temperature reading error makes everything else questionable.

Another thing to remember is that localized hot spots in the smoker could also create a situation where the temp probe says one thing and the actual temperature is something else. A remote reading thermometer can be placed in different parts of the smoker chamber to see if you have localized hot or cold spots.