And specifically, they are not confirming or denying that video fingerprinting are done.
What I think is likely is, as the paper states, that they fingerprint both audio and video. Upload both to their servers. But they end up using only the audio fingerprint for ACR. In this situation, neither LG's statement, nor the paper's statement, nor the GamerNexus folks's claims are incompatible with each other.
It even makes sense from a technical standpoint: it is far easier to uniquely identify content by audio than by video, as a fingerprint of a few milliseconds of audio is pretty darn ideal, compared to fingerprinting even a single video frame which has hundreds of ways it could be compressed depending on codecs, bitrate, resolution, etc.