I'd think the waveforms being "somewhat different" would be a good enough
confirmation, but if you have any music with exaggerated stereo separation
(my go-to example is the guitar solo on "Yours Is No Disgrace" by Yes...
woo hoo, stoner on the faders!) that should remove all doubt.
But if they provided any specialized recording software under Windows
(i.e., not Audacity), that's probably a good indicator that it's not a
standard USB audio device.