Actually 18 days?

The trip looks great, and I'm thinking about signing up for a January excursion, but in reading the itinerary, the "21 day" description seems pretty misleading.  The itinerary says that the "official" trip starts on "Day Three" and Day 21 apparently consists of an airport transfer (on Day 20) for flights leaving early in the morning on "Day 21".  I've taken Road Scholar trips, previously, that include transit days in the advertised time frame for the trip (a misleading policy, generally), but this one seems particularly strange.