The techniques are very different indeed generally speaking since the blade on a DE is perpendicular to the handle whereas on a straight the handle is in essence on the same line as the blade. When it comes to skin stretching, you do not usually do that when DE shaving partly because the guard bar located between the blade and the handle does that for you.
Now all we need is someone to shave half their face normally with a DE and then on the other side hand stretch the skin and use the same DE. Could help determine if there is something to a straight giving a closer shave.