I suspected that.
I do as kz1000 suggests, if not puller threaded holes, I don't like to use the whacko method either and I hope that not over 3 whacks gets it loose, but I use a brass hammer with the flywheel nut set flush with the top of the threads or end of crank. If the flywheel has partly sheared the key it will come off easier usually.
If 3rd whack don't get it loose I've used a propane pencil tip torch and warmed the flywheel little bit. Don't get the crankshaft hot, just get the flywheel warm, aluminum expands faster than steel so it don't take much warming of the flywheel out from the crank. Let it set about minute after warming before the whack or even let it cool and re-heat before the whack.
On some Homilites I can use flywheel puller screws into the starter pawl holes. I've seen some tough ones and the heat and cool will get the tough ones.
When you get it off de-grease and clean the crank and flywheel taper good. Some don't realize the key is only for timing the flywheel and proper torque of the nut is what actually holds the flywheel from shearing the key. Any oil/grease, etc, on the taper will cause a properly torqued flywheel to shear a new key again eventually, usually.