Posted 2013-March-12, 16:47
I agree that over 3♠, 3NT is a catchall bid (does not promise stopper in the minors). It mearly denies spade fit or better than normal hearts.
I also agree that 4m are control showing and spade fit, and the direct spade raise is no control in either minor but "spade fit" (sometime Hx is a fit here).
Having said that, I ran a bridgebrowser study of this auction. Surprizingly, an overwelming majority of the 3♥-3♠-4m bids showed a "second suit" with no spade fit. A couple of times this second suit was the better of two three card minors. So random players on BBO don't play it the way "I" do (or gnasher). For what it is worth, the few people who rebid 3NT with weak hands follow the no spade fit, no great heart suit.
--Ben--