- A sys admin will not be rolling out OS patches. The platform does itself. - Attackers typically use DoS to make a system unavailable, not just make it expensive to operate. I do note the cost concern, but if attackers are unsuccessful taking a system down, they are less likely to attack it. - I indeed meant "attacking through the OS is unreachable", referring to the portion explaining the OS patches are better managed. It's indeed not perfectly accurate phrasing, but allow a guy some literal freedom in the summary - the details came before.