I agree, because the inventory release dates are based on the individual Resort Calendars and the days of the week on which check-ins are allowed. The release dates are not the same across all resorts in the system.
Use this link to determine the exact date for your desired resort/check-in:
Inventory Release Calendars
(Note the link above is for Weeks usage. Anyone reading this who wants to check the release dates for DC Points usage should use this link (may require sign-in to my-vacationclub.com: )
Inventory Calendars