"What would a frequency response of a loudspeaker say?" Not much.
But, back 25 years ago the speakers I had had bass extension down to 45hz. I had heard a lot of other speakers/systems and knew I was missing that bottom octave. I thought looking for new speakers that went down to 38hz, 35hz, 30hz would have more bass. Probably. On the other hand, I heard of pair of small Sonus Faber that only went down to 60hz that were much better than the speakers I had.
Looking at the simple 30-19,000... was just a quick and easy factoid of very limited help in putting some speakers in the "maybe list" to seek out to audition, and other speaks in the maybe not list.
I did, with great trepidation, wander into a Bose store, the brand with no specs. The thing about Bose is that they become the most successful speaker brand in America, based on gross revenue.
One of the secrets to their success: Bose did not cater to audiophiles. It was the strangest visit to an audio retailer, even. I left the Bose store having been unsuccessful in listening to any of their "better" speakers in any meaningful way, and had no sense of what their base extension might have been. Or, anything else about the sound quality.
Trust your ears.