it is simply a different wiring option that a lot of people prefer, it is not necessarily incorrect. As I recall it goes like this switch 1 is split-off-on for the humbucker and switch 2 is on-off-phase for the single coil. This allows you to get coil split on the humbucker and still make use of phasing options using the switch for the neck pup. IMO he actually did you a favor by wiring it this way as it makes your guitar more versatile. As for the buzz, if it is more than the amount of buzz you get from a typical single coil there might be something wrong, the typical problem seems to be a grounding issue, but I couldn't tell you for certain how to confirm this.
