Mox,
Tiger is wrong here and so are you or anyone that believes the ball can be trapped between the clubface and turf in the swing. Just try something that Bill suggested earlier: Place a ball on a table then take a club, say a 7 iron and lay it behind the ball, now see if you can trap the ball between the surface and clubface, you will see that the shaft will need to lean forward past horizontal to do it.
You should read the link I posted earlier in this thread it shows and explains to you how the ball reacts to the clubface. The ball is in contact for half a millisecond as it is struck an oblique blow by the loft(not a downward vector), it is compressed onto the clubface, slides up then rolls before the coefficient of restitution springs it off.
Look again carefully at these videos: Does the driver trap the ball in the turf? does the iron? No! of course they don't but they all create backspin.
Tiger may be a great golfer but he does not necessarily understand the ballistics or physics of impact.
Mox, you are a knowledgeable golfer but please give this matter some closer observation and you will see that 'pinching the ball' is a myth and impossible.