I'll repeat the question asked below, because I guess Tatty Bogle can answer it. Is there a difference between the B and C rows on a BC box and JK's B and C rows?

I wonder - in the context of the thread - because if they are the same or similar then 'Irish' BC box player who wanted more options for the left hand could get such a box. And if they didn't then it would be their choice not to use the left hand that way. Though I guess the three-row boxes are set up to give a different sound.