According to their experiment, the best attenuation you can get out of any ferrite is a useless value in the single digit decibel range, which can be as poor as 0.5.
That's almost like saying these things don't work.
How ferrites work is that they are actually resistive at high frequencies (in addition to boosting the inductive reacatance of the conductor). How much attenuation that translates to depends on the circuit.
We wouldn't say that a simple resistor, as such, has a certain decibel loss of voltage; it makes no sense. A resistor can exhibit no loss of voltage, if the current flowing through it is negligible.
Ferrite beads work and how they work is that the target of the unwanted noise (the destination where we don't want it to go) has, at the given frequency, a relatively low impedance relative to the impedance of the bead.
E.g. suppose the noise faces a 10 ohm input impedance into the device where we don't want it to go, and the ferrite manages to create a 1000 ohm source impedance. Then we have a 100:1 voltage divider, which is a 40 dB reduction.
In my personal experience, the clearest directly perceptible example I've seen of their effectiveness was when I had serious noise on an LCD monitor due to a long serial line running under it between an embedded board and host. I had a clamp-on ferrite bead lying around and put it on the serial line. The display's obvious visual disturbances completely disappeared.