The ignition will fire at the trailing edge of the magnet with or with out a Syncro Spark.
BUT if you look at the signal line from a hall switch it is a square wave, the signal goes high at the leading dege of the magnet and low at the trailing edga. It is the duration of the square wave that the Syncro Spark calculates the RPM from. A wide magnet gives a longer signal
and the Syncro Spark says long square wave = slow rpm and it will stay advanced
THIS IS ROCKET SCIENCE