It took me a while, but I eventually decided that the correct way to interpret this is most likely that (1) small sealed subs usually have worse distortion than other types, and that (2) Revel is the name most readily associated with bad-sounding small sealed subs.
Sealed enclosures are generally smaller, so I suppose it is reasonable to combine small subs and sealed subs into a single type. But is it really reasonable to say that this type of sub typically has worse distortion than other types? The number of variables that will influence this is fairly large. Suppose we compare a sealed sub with a ported sub where both have the same size driver and where the linear excursion of the driver (Xmax) is the same for both. In this comparison you would expect similar distortion levels at a given SPL, except for the way that the port influences excursion. At the port tuning frequency, the driver will be nearly motionless, thus distortion from the driver itself will be very small at and near the port tuning frequency. However, the impedance to air flow in the port increases as the square of the velocity, and therefore as the square of SPL. This effect produces compression and thereby distortion, although it typically is not as great as what the driver distortion will be in a sealed enclosure for the same SPL and at that same frequency, the port tuning frequency. But then you have to also consider what happens at frequencies below the port tuning frequency. As frequency decreases, below the port tuning frequency, the excursion of the driver skyrockets, which does not occur with a sealed enclosure. In spite of the very large driver excursion, the SPL output from the speaker is low because the wave emitted from the port is out of phase with the wave from the driver (below the port tuning frequency; this is the reason that the rolloff of ported speakers is steeper than the rolloff of a sealed speaker). If the port is tuned adequately low it won't matter, however depending on the port tuning and on how low in frequency the music or sound effects are, the audible distortion from a ported speaker can be substantially worse than the distortion from a sealed speaker using a similar driver. This will typically only happen with a so-so ported sub and with movie sound effects (explosions), but in this scenario, with movie sound effects and a middle-of-the-road ported sub, the sound from the ported sub can be overwhelmed by the distortion.
And even if the generalization were a good generalization, it probably would not be fair to equate Revel with bad-sounding small sealed subs, in the way that you implicitly did. Revel makes one subwoofer with a single 8" driver, and it is sealed. They make an in-wall sub that uses a sealed enclosure, but it uses two 8" drivers, which is equivalent to a single 14" driver. They make a 10" sealed subwoofer, a 10" ported subwoofer, a 12" sealed subwoofer, and a 12" ported subwoofer. Six different subwoofers all in all, an only one of them would conform to the description of a "small sealed sub", unless you want to include the 10" sealed sub. I have not heard the B110v2, but in all reasonable likelihood and based on reading some of what went into its design and construction, I fully expect that it is a phenomenally good subwoofer. As for the B8, the most I would hope for is that it holds its own again other 8" subs similarly priced, which is to say that I would not expect it to sound especially good, however if it were ported and a little bigger this would not likely make it sound any better.