Allegedly it emulates the EQ that takes place when a cranked tube power amp drives a speaker cab, or rather the frequency response that may occur in said cab due to tube drive.
Other Bajaman's designs such as the CV30M1960A cabsim include a similar first stage that takes care of this EQ-ing, followed by other stages that emulate the frequency response of the speakers.
The following schematic illustrates better what I'm trying to explain in my non-native language:
"high end rising response" and "low end resonance", both features of a tube amp power stage (and further developed in the first schematic of this thread), followed by HF rolloff stage, MF dip, etc; which are the frequency response of a particular speaker or cab.
So a Presence and Resonance emulator would be really useful for those who like to experiment with several cabsims such as the Condor, Multicab, etc. Or, as said, pimp up our D Class Amps
In short, nope, not a cabsim, rather a pre stage for a cabsim: useful to get a more accurate/realistic tube-like response.
At least that's what I think it is...