While Logic says you have a Valid Deduction... John has it Nailed...
Can't help it goes against what we Deduce... it is a Fact.
Lots of folks Convinced Single Fire Ignition, and Hardened Valve Seats, and Huge Carburetors, and Bigger cams, and Oh yea... Drag Pipes... all work better than anything....
As an aside... I can guarantee and Show you right here in the Yard, that a 1994 FXR that is running rather well, with just a Change to Dragpipes [admittedly not tuned] will foul the plugs within 1/2 a Mile...
Switch Pipes, and [if the plugs are Champions] clears right up and has great manners besides.
Note I did Not specify Stock Pipes!!!!!

 

Certain conditions can fowl a plug and high speed heat can coat tip with a almost clear glass like insulator.
Had in happen I a new truck that had the vacuum operated secondary back barrel of the carb that as vacuum dropped, it let a stop drop out of the way and the linkage picked it up.

It was bent at assembly. This made engine lean at high speed. When it started missing, took it in. They spent days trying to fix it. Even called in the factory before figuring it out.
Seen it happen same thing in a FI German car.

 

these are the ones but however I use ap 985

Autolite 4265, Champion RN12YC, Harley-Davidson 5R6A, and NGK BPR 4ES