You can request a specific phase, but I don't think you'll know until check-in if they are able to accommodate.
Sometimes they are flexible at check-in as well.
It will depend on availability (holiday weeks will be full with Owners who have guaranteed units) and what specifically you have reserved. Example: not every phase has a one-bedroom or a two-bedroom lockoff.
Apparently different sections/buildings have assigned days of the week for checkin/checkout. I'd have to see if I can find it again, but there was a map showing which buildings turned over on Fri/Sat/Sun.