A good manager will keep an employee engaged, challenged, and happy. In fact managers can achieve this even if the company itself is not engaged, challenging, and a happy place. Good managers can also shield employees from an array of terrible dysfunction at the company level. All good managers I've ever had have this skill. A bad manager will not only expose company dysfunction, but magnify it, making the employee's job more difficult than if the employee has no manager at all. I've had the latter several times, and it's soul-draining.
The rest of the article reads like a novice's take on the SF startup scene, which I happen to loathe anyways. One funny example is the #7 HR comment, which exposes a pretty big misunderstanding about HR. HR serves no useful purpose to the employee; it exists to shield the company from problems, nothing more. Improving HR will have no meaningful impact on employee retention.
<Edited for tone.>