Question regarding why some info on Performance using Objects For In Loop was not mentioned in this video?

Hi, after looking at this video, I went on to read a little online about it to help fill in some gaps. Then I noticed a note on performance that seems to be important. It suggested to always use the .hasOwnProperty method when using for-in loops, in order to make sure you loop through the the actual properties key-value pairs your calling and not any of the built-in object/meta-information the parent object has by default.

So I am wondering why something like this would then not be mentioned in this video?

His example of:

var person = {
name : 'Sarah',
age : 35
};

for ( var key in person ) {
   console.log( key, ': ', person[key] );
}

Apparently, would have been improved if it was written as:

var person = {
name : 'Sarah',
age : 35
};

for ( var key in person ) {
   if ( person.hasOwnProperty(key) ) {

   console.log( key, ': ', person[key] );
  }
}

Link with more info on Mozilla: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty

Also Is this .hasOwnProperty() method something I should always use in for-in loops or should I only use it sometimes?