Sure, but suppose it's 360 Y passengers across 36 aisles for the 777, and 180 pax across 30 aisles for the 737. It's still going to take less time to board the 777 as there are fewer passengers per aisle per row, as what slows things down is each passenger stopping to load their bags in the overheads and move into their seats. You do that less times per aisle in a widebody, thus they load faster. (This is assuming front door loading for both, noting that the wide door of the 777 is not a limiting factor normally even if only one is used.) If you've ever taken a domestic A330 in Australia you will see they load way faster than a 737 (from front door only), as they have only 4 passengers per aisle (8-across) versus 6 passengers per aisle (per row), a 50% increase in theoretical loading speed.
