At first I thought this might be regenerating A/C to provide a super clean new sine wave A/C output, like the PS Audio Perfectwave. However, the "sinewave" part of the name refers to the waveform when this is on battery power. Apparently other battery backups do not produce a sine wave A/C output when on battery power, and so they don't work with some types of devices that might plug into them.
The CyberPower does filter the A/C coming in, and protect against voltage sags, so it's cleaning up the sine wave A/C power coming in. I went ahead and got one for my Schiit Yggdrasil. I've also found DACs not to sound as good with the UberBUSS (which I use just for amp and preamp).