I have not heard of that, is that two plugs per cylinder (8)?
Edit: I have heard of this in aviation engines, appears that these in vehicle engines are to ensure more complete and even burn?
AI states: Engines use two spark plugs per cylinder primarily for more complete and efficient combustion, leading to better power, fuel economy, and lower emissions, while also providing critical safety redundancy, especially in aircraft, where a backup plug ensures the engine keeps running if one fails. This dual ignition creates two flame fronts, ensuring rapid and even ignition across the entire fuel-air mixture, preventing hotspots and misfires, particularly in complex cylinder designs or at high RPMs.