Cutting at an angle to the blade is what gives you a radius larger than the blade radius. If you fed the stock at a right angle to the blade (very dangerous BTW), you would get the radius of the blade. As you move the angle of feed closer toward parallel to the blade, the radius increases. The blade is kept at a right angle to the table always. That method has been used for a long time to make mouldings. It can be done pretty fast, but you will still have to clean up the surface.
To do it like the safety-planer method by tilting the blade, you would have to be feeding the stock at a right angle to the blade, which is a good recepie for a nasty accident. It would also take longer and cut rougher than feeding at an angle to the blade. But if you really want to use this method, the safety-planer would be a safer and cleaner way to do it (other than a purpose-made moulder as Spoke mentioned).
Though, I have to agree with Mattia about just buying them. The value of my time making blocks with any of these methods is WAY more than the $10 it takes to buy one already done. And I can buy a whole set of blocks for the cost of a safety-planer (since I don't already have one).
It's a good method to have in your bag of tricks though.