I am assuming he is a very early beginner so I doubt he is adding his ring finger in on the B string, If I am wrong and you are consider not doing that. The G is a lot easier if you only have to work 3 fingers then 4 for the extended version. If you are following the beginner module I know for a fact that Chris only shows the open G chord in it's simplest forms.
Until you get in to more intermediate/advanced guitar playing you will not absolutely NEED that anular adding to the G. It only really makes its way in when you start playing suspended chords like a Gsus2. sure there are a great deal of songs that do add the anular to the Gmaj but you not adding it for the sake of getting the change down is not going to break the song for a beginning player.
God said to Abraham, “Kill me a son”
Abe says, “Man, you must be puttin’ me on”
God say, “No.” Abe say, “What?”
God say, “You can do what you want Abe, but
The next time you see me comin’ you better run”
Well Abe says, “Where do you want this killin’ done?”
God says, “Out on Highway 61”