See, that's the point I'm trying to get at. How did you come to think of dropping the main? That's not a obvious adjustment to make.
@Will Gilmore:
You look at the shape of the sail. It helps if your sail has draft stripes.
RAther than the concept of "dropping the main", we should think of the concept of "easing the luff tension". He eased the main halyard, which reduced the tension on the luff. Easing the main halyard or easing the cunningham are very similar. They both reduce tension on the luff.
Luff tension controls the forward and aft position of the draft. By easing the luff tension, he moved the position of the max draft aft. A tight halyard pulls the max draft position forward and makes the entry of the sail more rounded. A very forward draft with a rounded entry on a mainsail might be at around 34% of the foot. A looser halyard has the max draft further aft, and the entry is "finer". A "fine" entry would be pointy-er, with the max draft as far aft as 50%.
A rounded entry with the draft relatively forward has a wider groove. It is more tolerant of steering and trimming errors because it is less likely to stall. It works across a wider range of angle of attack. It is better for acceleration, and punching through chop and waves. It's sort of like driving in a lower gear.
A finer entry is faster, but less forgiving.
(BTW, outhaul tension makes a difference in the bottom section of the mainsail. More tension on the foot flattens the foot and moves the draft aft. Full length battens really reduce your ability to shape and move the draft too)