No Voster is speaking clinically about delusions which must cannot be physically true. Someone can have the misconception that their husband is cheating on them every night with a different woman and they may be wrong or right as it is a possibility. So it is not in the world of psychiatry considered delusional.
Now on the other hand if someone thinks their husband is having relations with a gerbil on the moon every night and sending her video tape of the event, that is delusional.
It is within the laws of physics that the police are out to get Oscar so it is not considered a delusion.
It's not within the laws of physics that the gun went off in the Tasha without him pulling the trigger, so how is that one explained?