But it doesn't. There are plenty of people with CS or SE degrees that lack a minimal level of understanding. Even with a terribly lenient definition of minimal.
I'm talking about people who get through 4 years of a decent CS program and would vehemently insist that "array" is an exact synonym for "linked list".
I'd say that the benefit of a CS degree is weaker -- just that it brings forced exposure to important topics, so if you have two people who are smart, the one with a CS degree is going to be more well-rounded. The thing is, you usually don't get to decide between two smart people when hiring. And the CS degrees that are around don't seem to reduce the risk of bugmaking.