Yes stereo subwoofers would be the best application for them, the sealed enclosure controls cone excursion well so a crossover is not needed for them but if used would increase power handling and output capability.
This got me thinking on a bit of a tangent.
A lot of us use ported speakers. Now ports have resonances that often show up in the measurements.
With
subwoofers, we normally take care to avoid exciting these port resonances, by low passing an octave or so below it.
Yet so many of us use ported speakers as a whole, and don't really "notice" the vent resonances, even though they show up in the speaker's pass band.
Additionally, vents introduce some phase shift, which makes aligning to subs that much more difficult.
So shouldn't more speakers designed to be used with a sub be sealed, and and subwoofers likewise (or with a passive radiator, not a vent, to avoid the vent resonance?).