It doesn't really matter if a basshorn is really a tuned pipe, because it is just a label. It's just a matter of semantics. But it might be useful when looking at one way instead of another for critical analysis.

I've often said that most basshorns are too small to be true horns. I've observed that the reactance measurements show them to act like tuned pipes in the region they're used in. The mouth area is small, and the impedance curve is peaky. It just looks more like a resonator than a horn to me.

Maybe this feature should be embraced. Maybe when the device must be made physically small, the best approach would be to try to align the system like a tapered pipe, where driver position in the line is used to set standing wave modes for smoothest response. Seems like a good idea to me.