Separate coil, separate ignition module - not what I would consider a magneto?.
But in any case, we're talking about the low voltage wires coming from the alternator.
Not a magneto, as they generate the spark directly, all the Triumph is doing is removing all load, and feeding the ignition coil directly from the alternator/rectifier.
BTW, what Triumph did you have? - strangely enough on the way back from work today I saw a guy sat on an old Triumph Speedtwin.