Looks like delaminated carbon build up and not pitting to me. Carbon is self limiting in its build up most time and flakes off looking like what you see.The complaint of performance is that it will ping on the manual recommended 87 octane fuel and I have to run 89 or 92 to eliminate it. You don't have any concerns about the pitting looking marks in the valves?
FWIW, did the plugs on my then 2020 3.6L Gladiator at 60K and bore scoped the plug holes also and had very similar but lighter carbon build up build up. I also run a fuel cleaner about every third tank and do a Seafoam treatment every 30K miles also.
You get random misfire codes? What application your engine in?