Wait, is your question serious, and people talking about it being in jest directed at my comment and not the one above it?

How often do you think the OP's "functional" team fixes small problems with their code before they become large problems? How often do you think they discover small features that lead to huge gains but need a developer's understanding of sized to discover it's small? And also, how often do you think they get stuck creating nearly impossible features that can be worked around with a small amount of work from the users that they would rather not do?

And none of those is the large issue anyway. The large issue is that teams working like that can barely create any software, for much more complex reasons than fits in a comment.