@Varler the (current) Object Class ratings have no basis on whether something is good or bad, only on how easy it is to contain it.
As stated on the
Object Classes page:
The Locked Box Test is an informal guideline used to determine an object's most appropriate Object Class. It goes like this:
> If you lock it in a box, leave it alone, and nothing bad will happen, then it's probably Safe.
> If you lock it in a box, leave it alone, and you're not entirely sure what will happen, then it's probably Euclid.
> If you lock it in a box, leave it alone, and it easily escapes, then it's probably Keter.
> If it is the box, then it's probably Thaumiel.
So while this one is classed as Keter because the SCP foundation themselves can't contain it, they treat it as effectively "self containing" because it only appears to people who are alone & about to die, and as such they can't spread the knowledge of his existence.