Witnesses are direct evidence (as Wikipedia says and you just quoted). We will never have the mechanisms for "testing" evidence here on websleuths. The jury will decide, if this gets to a jury. Meantime, as Wikipedia also says, only *some* evidence is "anecdotal." Again, juries get to decide - groups of people.
You've made your decision, apparently. You have your own ideas about confirmation. To me, this witness provides a provisional hypothesis, which is way better than no witnesses. Sometimes, two witnesses are no better than one (if they're wrong). But this gives a place for LE to start developing how to go about finding out what happened to Paighton.
It's good to have at least some good will toward witnesses, because Lord knows we might all be a solo witness to something (and many of us have been) and if we're to be disregarded routinely by others, it gets harder to speak up. LE will sort it out.