There always needs to be a separation from hv generated by the secondary output coils and the pick up coils elv and associated wiring due to inductance . In other words........you don t want false triggering of the ignition system .
Aside from this ......the 3 main reasons I see the mounting position on the rear guard of the tci as one to isolate it far away from the heat of the motor as well as electrical interference and a water resistant location .....not a poor choice at all when taking all into consideration .
