Better than HTC design which traditionally uses pounds of glue and insulating tape.
I'm fairly certain the vibration motor is the other component that was not removed from the rear case. http://imgur.com/Sm9Ybn0
It appears to be mounted in the rear frame of the device. They didn't remove it or the main speaker from the rear frame nor did they remove the earpiece speaker from the midframe.
I'm 99% sure that the vibration motor is the part I indicated in this photo: http://imgur.com/Sm9Ybn0
Looks like it's probably the rectangular coil to the left of the IMEI sticker on the metal portion of the body.
Edit: I don't see any way it connects and looking again those may just be cnc mill marks, so maybe it's a part of the plastic camera surround that has multiple spring contact points.