the enchanted texture of the pumpkin concerns full item slot...,
not the pumpkin itself... (as an example an enchanted book or a enchanted tool)
how to create the "bug".:
1) take an enchanted book with curse of binding, an anvil and a carved pumpkin
2) enchant the carved pumpkin
3) drag the item over a monochrome surface as in the picture
=> you will see the entire slot is enchanted, not only the pumpkin