It counts in the brochure number, which is exactly why that number misleads. A 10 or 11 day voyage includes about four days crossing the Drake, leaving roughly four or five days of actual excursions. When you're comparing trips, count landing days rather than total days, because that's the thing you're really buying.
Run the comparison and it usually flips your ranking. A 14 day voyage gives you closer to double the time on site than a 10 day one, because the Drake overhead is fixed regardless of how long you stay.
None of which means the crossing is wasted. It's when the lectures happen, when biosecurity gets done, and when albatross and petrels follow the ship. Fin and humpback whales turn up on good days, and there are dolphins and penguins as you leave the Beagle Channel. But it isn't a landing day and you shouldn't pay for it as though it were.