Being "friendly" and "well-liked" sound like the kinds of goals children would come up with on their own because they crave attention and positive reinforcement, not what adults should be teaching them.
The specific instruction is "how" to accomplish that goal, not that the goal exists- obviously, the goal exists for the reasons you specify. The difficulty is how to get there, which is extremely hard, doubly so for a brain that doesn't necessarily have the archiecture required for fully understanding the restraint, thoughtfullness, empathy, etc. of being friendly/well-liked.
The ability to be friendly in adverse situations is absolutely a social skill. I have a couple of coworkers that have the ability to remain friendly even in intense situations. I find it really helps deescalate situations (or keep them from escalating in the first place) without derailing the conversation.
Still, being "friendly" and "well-liked" is an important skill for later. People tend to not want to work or have sustainable relationships with people they can't stand.
It's probably poorly phrased, but I think we've all met people who just ∂on't really know _how_ to be a friendly, approachable person.