Hey Doc,

Thanks for the heads-up. I'll double check, but I'm pretty sure the 4 strings is referring to the fact that the early version of the G-chord is only played on the top 4 strings (with the only fretted note being the 3rd fret of the high E-string). That's most likely where the confusion is coming from :) 

Feel free to post over in my forum if you have any other questions along the way! 

All the best,

Anders