[util.smartptr.shared.general]/6:

For the purposes of subclause [smartptr], a pointer type Y* is said to be compatible with a pointer type T* when either Y* is convertible to T* or Y is U[N] and T is cv U[].

IIUC, P0388R4 makes "pointer to array of N U" convertible to "pointer to array of unknown bound of (possibly cv-qualified) U". Hence, the definition is now equivalent to "Y* is compatible with T* when Y* is convertible to T*".

Does it make sense to strike this definition of "compatible with" and replace its use with "convertible to"?