Ever measured the bores in a SB Mopar before and after installing a torque plate? I have. There is a lot more distortion than you think.
It's all about sealing the combustion chamber as best you can. Remember, the rings & cylinder are the bottom of the combustion chamber. Striaght, round bores are key to making a good seal. The best way to do this is to use a torque plate. Yes, it's not exactly the same as having a cylinder head on the block, but I don't know of any special hone that will hone a bore with the head installed. ;)