This is somewhat true, but there are caveats:
- The discount must apply for your dates, resort and room type.
- Not every room, date, resort will be eligible.
- Every room booked from inventory reduces the number of rooms eligible for discount, since discounts exist to fill rooms.
- The discount is not really applied to your existing booking; your booking is really cancelled and rebooked.
If you will not travel without a discount, it's not recommended to book before the discount comes out. You need date flexibility, resort flexibility and you also need inventory to be offered.