Modern efficiency standards are anechoic @ 1m (if they can be trusted).
The simple fact is speaker size goes up with efficiency and also
with the the bass extension, that is why PA speakers with high
SPL and efficiency are poorly suited to domestic environments.
But for a low power amplifier domestically they do make sense if
you can live with the size of the speakers. Also high sensitivity /
SPL speakers have lower distortion generally for the same SPL.
If the numbers are true they will have b****r all bass for their size,
that is just the physics, and the apparent construction would agree.
They would be great for period equipment and recordings IMO.
For modern stuff to keep up with them (with 10W to 20W)
you would ideally need two high powered subs, run higher
than usual (presumably) and because of that run in stereo.