> But it didn’t make any perceivable difference in real usage.

It can, it depends on the systems and user patterns. Example: if an end user is going to the same site over and over, those DNS responses are probably cached locally on the device, and may also be cached on any upstream resolvers. OTOH if you were somebody without a Facebook account that went to Facebook.com to view a post from a link, you could easily have 120 different DNS lookups for various resources on that domain that haven't been DNS or web resource cached yet.