Had a 93 mustang with a 8-plug 2.3 (dual coil packs). Think the 2nd set of plugs fired a little later - meant to scavenge unburnt fuel. Pretty crowded changing plugs!
Popular Myth that came about because of Waste spark systems, I read this all the time, its just thought of as common knowledge now, lol
Fact is, it was easier to time distributorless engines by sparking each cylinder at TDC regardless of compression stroke or exhaust stroke
So thats what "they" did, the spark on the exhaust TDC is "wasted", hence Ford's current name for this type of system
Spark at the end of exhaust stroke can't clean up anything, think about it, a spark plug has a hard enough time igniting a good air:fuel mix under high compression, it wouldn't have a chance in hell of igniting exhaust, even if there was a misfire and air:fuel mix was still present
The very first gasoline and spark engines used same setup, and your lawn mower and most single cylinder 4-stroke engines do as well
The "points" or ignition module runs off crank shaft, sparks every TDC, and not for lower emissions
, just simpler to do it that way