The month is the peak for so many tourists, hence the stricter conditions. Quite common in this business.
April is;
cherry blossom season in Japan.
long Thai holiday season (Songkran), so lots of Thai tourists expected.
school holidays in Australia (and Easter holidays too), so lots of Aussie tourists expected.
among others.

So, the hotel expects high occupancy that month, but since it cannot/will not outrightly block points awards (like some other hotels unscrupulously do), they add cancellation restrictions.
FYI; I am writing this from Bali, where Courtyart Bali cancellation deadline policy is 1 month for December, but only 1 day in January....the season matters.

So, either lock in your trip and the award, pay cash, move your trip to March, or stay elsewhere! You still have many choices.