Historical Rules · 13 July 2013
Rule 708.6b
Official source text from the 13 July 2013 Rules release
Anything that performs a negative comparison (such as asking if cards have different names) involving one or more split cards in any zone other than the stack or involving one or more fused split spells also gets only one answer. This answer is "yes" if performing the analogous positive comparison would return a "no" answer.