If a little patch introduces a problem, they have a way higher chance of finding what caused it by examining said little patch and are able to fix it faster. If a big patch brings any number of problems that are not directly apparent what caused them, they have to look at everything to find out what caused the problem, taking way longer (For how many days did the backend error survive that came with 1.1? Right, its archived. Almost 2 weeks) For reference:
Patch 1.1 on May 31. : [PC] - Vermintide 2 - Patch 1.1.0.1 Content Update
Patch 1.1.0.3 on June 12. : [PC] - Vermintide 2 - Patch 1.1.0.3