Why does utils.appendChild allow an empty parent array?

[pgoldrbx]

When writing tests for the utils methods, I came across some logic that was confusing:
https://github.com/benjycui/jsonml.js/blob/master/lib/utils.js#L132

} else if (child || !parent.length) {
  // append
  parent.push(child);

This allows for some unclear behavior, particularly when allowing exception for a parent with no length.

1. append a child to an empty parent array

const jml = [];
utils.appendChild(jml, '');
// jml === ['']

const jml = []; 
utils.appendChild(jml, ['p', 'hello']);
// jml === [ ['p', 'hello'] ]

Is this a real use case or an edge case bug? I'm guessing this would never be desired and should probably not be allowed.