Safety wire is used when a locking tab can not be used. The desire is to prevent the bolt or nut from rotating in the direction of loosening. A single strand through the hole is strong enough. Using two, twisted strands allows you to encapsulate the fastener, and gives a more rigid link between the two fasteners. Encapsulating the fastener also eliminated the small amount the fastener could turn with a single thread of wire.
While a single wire would prevent the fastener from falling out, it will not prevent the elongation of the hole.
The direction of the wire must be such that the loosening fastener pulls the wire tight. If there is slack in the wire, or the direction of wrap is such that the wire can give, the locking of the wire is defeated.
road racing motorbikes requires almost as much safety wire as aviation. Hope all of you are well.