I'm not sure I understand the question? Are you asking why using the same SoC as the iPad 5 is an option?
If so, it's potentially because it could cut down costs from only producing the one chip as opposed to two. If not, clarify please.
Sorry, wouldn't**, I was tired last night lol. Why wouldn't they be able to put the same chip in both, with the mini's A7 clocked lower than the iPad 5's?