When Bosch was heavily advertising their +4 platinum center sparkplugs I bought eight to try on a 1995 360 V8.

These had 0.066 gaps but the four ground electodes "probably" helped reduce peak firing kV by allowing the hotest, most shielded, or sharpest edged ground strap to accept the most favorable ionizing.

The Bosch+4 plugs definitely pinged more on hot summer days on 85 AKI gasoline and a 205 degree thermostat.

When a Mopar Performance JTEC PCM was swapped in and 93 AKI fuel was used they pinged even more. Not even Sunoco 96 AKI gas would stop the pinging.

My guess is that this indicated that a big gap did advance the "real world" ignition timing.
Perhaps a 4 degree advance or thereabouts.

I found no fuel economy gain with these Bosch+4s in single truck 304 mile tests over the same highway but in fairness to Bosch a much more sensitive test like a SAE/TMC Type IV two truck test is probably a necessity to reliably find 2 to 4% gains like Bosch was claiming in writing.

I seem to recall that for warranty claims purposes automakers routinely retard timing on factory vehicles about 6 degrees from what their in house testing shows a blueprint engine could operate on without ping.

It would be interesting to set 7 old style sparkplugs like Autolite 3023s to gaps of 0.025 inches, then take an Iridium tipped spark plug with a gap of 0.080 inches and try it sequentially in all eight cylinders. You might find both the most troublesome cylinder(s) and also make a guess as to the timing change that an extra 0.055 of gap gives.