Unusual Hemi Timing Setting....

I don't have first-hand experience with 2G Hemis but some thoughts on why this particular one requires such low ignition advance... Mostly pertaining to how it's a big stroker engine; strokers in general need less advance due to the rod-length-to-stroke ratio being lower. Also because of the longer stroke the dome on the piston doesn't need to be as big to have decent compression so it probably doesn't obstruct flame travel like on a stock-stroke 426 Hemi. Since the spark plug is near center of the chamber the flame doesn't need to travel as far which we all know is an advantage of Hemi chambers.

Quick web search found some forum posts of guys with big-inch Hemis having 32-34* total timing but they were in the 572-605" range which I believe has a bigger bore than a 512 would, if the 512 is based on stock-ish bore size. IIRC much bigger than that needs the Mega block with the oversize siamese bores which would then of course require more ignition advance.