I'd agree with you - those are too far off to be considered idem sonans.  If it were me, I'd be inclined to tell them that I'd be happy to search any names they provide... for an extra fee, of course.  But, it isn't your job to guess which names they think are sufficiently close that you should just know to check them. 

Let them know that you understand the rule of idem sonans and that you believe that you are already doing a sufficient search.  If they want more, they should have to give you specific names to check.

Do clients have nothing better to do than make up their own title standards? 

Best,
Robert A. Franco
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