I don't think that is the case, or atleast that has not been my experience. Most teams would be happy if you do these, but not affecting the next deliverable. So if you are willing or can spend extra hours that becomes manageable, but one can't always be in a position to spend more hours working (priorities, family etc.). What would be best is team encourages your involvement and factors that in deciding the target date of your deliverables. This would win for both since knowing domain makes one to understand the problem better and program beetter.