Hi Sunnyboy !
Any hits on your guitar slowly damage your guitar, just look at Tommy Emmanuel or recently Jon Gomm to realize how wounded their guitars are š
About this video, he could have use the side of the guitar to reach the rimshot, but the trick is nice ! plus, with a ring the sound is sharper.
There is no name for this percussive hit, it’s part of the percussive acoustic style, you can basically hit everywhere you want as long as it gives you what you’re looking for (in this case, he doesn’t have to reach the sides so he can spare precious time and last a little longer on tap chords)
You have other examples like Antoine Dufour’s song These moments :
http://www.youtube.com/watch?v=YQlyHbu0zz4
He’s hitting with the nail to create a kind of high pitch rimshot.
š