Does that actually work though? As far as I can tell the string representation of GenericEntity.NULL_FIELD is "[null-field]" and not "nullField".
Assuming it does work, is it really worth adding something that is more verbose than the existing method but achieves the exact same thing?
Do you really prefer:
<set field="parameters.statusId" from-field="nullField"/> <!-- or [null-field] -->
<set field="parameters.statusId_op" value="equals"/>
<set field="parameters.statusId_op" value="empty"/>
If you do that is fine, go ahead and leave it in there, it's entirely up to you and Hans.