Ask HN: In JavaScript, changing the value of an array item not advised?

I'm reading through jQuery Fundamentals (http://www.rebeccamurphey.com/jqfundamentals/#javascript-basics.examples.change-array-value) and this tip in the JavaScript chapter surprised me: While it's possible to change the value of an array item as shown in Example 2.28, “Changing the value of an array item”, it's generally not advised.

I wouldn't think just changing the value of an array element could cause a problem. Is this truly inadvisable or was this written in error?