Hey Sweep in sleep,
I actually copied this answer from another post with a similar question. The following was Neal Walter's response, and I thought this may explain how the songs are selected. The question was about a specific song, and here is Neal's answer.

Hi,

Guitar Tricks will teach you the skills to learn any song on your own. Since we make the song lessons from an approved list we aren't able to take song requests.

I hope we get some more of your favorites, as were all working very hard to get more songs done. The site has many other lessons to teach techniques used to play many songs. You may hear things that sound familiar in many of these lessons, and say to yourself so that's how they're playing that.

One other thing, even the most simple lesson could be applied to hundreds of songs. I know you want to learn songs too, but don't forget about the way that the songs are played. You can use these methods in other songs too, all you have to do is listen for the similarities.

I hope this helps, and let us know how you're doing.