Why are Papaya and Data Palm plants said to be dioecious whereas cucurbits and coconut palms are monoecious, inspite of all of them bearing unisexual flowers ?

Papaya and date palms are dioecious which means male and female flowers grow on separate plants, so each plant has only one type.

Cucurbits and coconut palms are monoecious – both male and female flowers appear on the same plant, even though the flowers themselves are unisexual.

The key difference isn’t whether the flowers are unisexual. It’s whether both sexes are on the same plant or on separate plants.