Drag and drop spec allows multiple values for dropEffect which might cause browsers to behave differently.

[ragoulik]

The drag and drop spec specifies that UAs can choose the value of the dropEffect attribute from multiple possible options in certain cases. For the dragenter and dragover events, dropEffect is set based on effectAllowed, which can include multiple possible effects (https://html.spec.whatwg.org/multipage/dnd.html#dropEffect-initialisation). For the dragend and drop events, dropEffect is set based on the current user selection and the spec allows multiple possible effects under certain conditions (https://html.spec.whatwg.org/multipage/dnd.html#current-drag-operation:~:text=Set%20the%20current%20drag%20operation%20to%20either%20%22copy%22%20or%20%22move%22%2C%20as%20appropriate%20given%20the%20platform%20conventions). Should the spec be updated to specify a particular dropEffect value that UAs must choose in order to guarantee interop?