With wasted spark ignition - single tip spark plugs are preferred so it does not create weak and stray sparks, When a combustion event is about to happen there is tremendous compression in the cylinder and the coil has to unload its charge to ionize the compressed air between the spark tips. The other side should not be fiddling with discharging this buildup by fooling with multitips as the polarity of charge swaps around between the loaded and exhausting cylinders.
-- need some coffee to understand this
Gap erosion can be controlled by manufacturing plugs with precious metal tips