Is a “lock of hair” necessarily separate from the rest of someone’s hair?

I'm not sure why Wikipedia says that.

Traditionally, a lock of hair refers to hair that hangs together. The word lock has been used this way since Old English ("lock, n.1," def. 1a in the Oxford English Dictionary). While locks can be cut and collected, and lock of hair most commonly specifies such severed clusters of hair, lock of hair can also refer to hair still connected to the body, if a single lock is distinct from the rest. That terminology applies whether or not the lock is alone on the head:

She lay on a couch with her feet up, twining a limp lock of hair around her finger and telling Mary about someone named Brady. (Anne Tyler, The Clock Winder)

Lock of Horus - a lock of hair that was left uncut over the right ear of young Egyptian boys. (The rest of the head was shaved.) (Allison Lowery, Historical Wig Styling: Ancient Egypt to the 1830s)

To add more realism to the hair, a hairstyle feature, such as a ponytail or lock of hair, can be animated independent of the rest of the hair. (Rick Parent, Computer Animation)

Even Wikipedia editors use it:

A kiss curl describes a lock of hair curling onto the face and usually plastered down (Wikipedia, "Kiss curl")

The lovelock was a long lock of hair, often plaited (braided) and made to rest on the left shoulder (the heart side) to show devotion to a loved one (Wikipedia, "Lovelock (hair)")