java 8 optional generic strange compilation error

Question

Here is a piece of code that shows a compilation error that I cannot really explain.

List<?> another = new ArrayList<>();
List<?> nullableList = null;

// this Actually works
Optional<List<?>> a2 = Optional.ofNullable(nullableList);
List<?> result = a2.orElse(another);

// THIS IS NOT ALLOWED!!!! COMPILATION ERROR
Optional.ofNullable(nullableList).orElse(another);

This is the description of Optional.ofNullable

@SuppressWarnings("unchecked")
public static <T> Optional<T> ofNullable(T value) {
    return value == null ? (Optional<T>) EMPTY
                         : new Optional<>(value);
}

In our case, T should be List<?> so why is it not allowed to do Optional.ofNullable(nullableList).orElse(another);

If anybody can explain why the "two steps" is allowed and why the "one step" is not, that would make my day. Thank you.