Well, he has to be diplomatic. He couldn't very well say working with Kenwright wasn't an attraction when it was put to him in such a leading way. That said, and as he stated, control over a club is very important and he had that at Swansea and Wigan. For a manager at Martinez's stage of career Everton and Kenwright are a perfect fit: a leap up from Wigan in terms of player quality and status in the game, and a chairman who wont panic and get shut to appease doubters if 'the project' started off on the wrong foot. 
But while things are fine now, I can easily see friction in the future when Martinez is able to smell success but not able to taste it. He's in the middle of his second transfer window and surely under no illusion about restraints in the transfer market to achieve what he wants with us. I'm sure he'd like a happy medium between a megalomaniac billionaire and a financially limited paternalist owner like Kenwright.  I dont think many are knocking about though.