The short answer to your question is YES they do make changes throughout the model year. The more accurate answer is they do it as they see fit. If there's a safety problem it gets handled immediately. If it's a change that makes the manufacturing process easier and more profitable it usually happens during a scheduled break in production. If it's merely a convenience item it'll be during a model year changeover.
Having said that Winnebago completely designed the exterior of the Adventurer part way through the 2013 model year. The ones built before October 1, 2013 look like the 2012 models. The ones built after October 1st look like the 2014 models.
The disappointing thing is they don't change the online or printed information to reflect the changes. If you call and ask specifically what has changed since the initial production began for a particular model they will give you the details.
