I think the problem os being only a single witness claiming to have sighted them? The Loch Ness monster has more reported sightings, so a single witness, imo, is not enough to say with a large degree of certainty that there is a big cat roaming around.
I’m not saying I believe there is a big cat roaming but it’s still unfair to say there’s only been one witness when this is something frequently reported on by multiple unrelated individuals.