Yes, this tutorial is specified for vanilla percussions in Addmusic, since I see there are lots people don't really understand about how that trappy stuff works.
When porters talking about percussion notes feature from other sound engine (eg. Square Soft and Hudson Soft's one), N-SPC does have the same feature, including SMW's. It's pretty limited, since a percussion note in N-SPC is only tied with corresponding instrument. And for whatever reasons, the original Java Addmusic's author decided to handle the percussion in a really confusing way. For backward compatibility, all Addmusics have to do that in the same confusing way.
The reason that @2X instruments stand out from other vanilla instruments is because how Addmusic handle it. @10, @12, etc. will not be covered here, since they are just standard instruments technologically.