Isn't this just ordinary politeness?
I can believe that it's not as common as it should be but it's what I usually try to do when asked a question I can't answer. Of course the amount of effort I put in depends on how important I think the question and answer might be.
Putting it into physical space, if someone walked into the wrong office and you told them what the right office was and how to get there that would generally be considered polite. Just telling them they’re in the wrong office is probably impolite. The warm handoff is the equivalent of walking them down the hall and telling the people in the other office why you brought them there.
Having worked at a high-end hotel and on software teams with high support standards, this is very natural to me. It isn’t for others.
Bad experiences when trying to be benevolent really take a tole on some people.