Greg, it's been my experience that since most golfers have no idea where they are aiming their putter, the stroke becomes appropriate for where they aim. In other words if they aim left they will manipulate the stroke to get the putt to go right of their aim.
I agree with Geoff that most putters are designed to "open" during the putting stroke, but if you would see how far many people aim their putter left or right (as I have via laser testing) you would see that it is more likely that the aim bias is causing the stroke vs the putter design causing the aim as compensation. Also, if the putter design is impacting the aim, how would you explain the players who aim right with the same design of putter?
I think that Geoff would agree that the amount the putter face (of these style of putters) is "opened" during the stroke is not significant and can actually be contolled by your grip pressure as Geoff teaches.
As most things are with putters, designing a putter for "most people" who happen to aim left is not the right way to do things. What about those who aim straight or aim left?
Andy Thompson
Totally Driven
Putting Zone Coach
Edel Putter Fitter