I've always idled my engines to shut them off, but when I got my Husqvarna with a Briggs, the manual states:
- Move throttle control (D) between half and full speed (fast) position.
NOTE: Failure to move throttle control between half and full speed (fast) position, before stopping, may cause engine to "backfire"."
They weren't kidding! Big boom at idle.
Lord, it's hard to change a 55 year old habit!!
Just a guess but I'm thinking there must be a anti backfire solenoid on your husqvuarna's carb. I'm guessing they want the engine to turn over a few times to evacuate any unburned fuel after the solenoid cuts off the flow.