Sorry, personal experience says you're wrong. My window is flat, and it is HOT when I get between it and the sun when the angle is right. There are a ton of articles on this.
For a FLAT window -
If you get between your window and the sun, your window is shaded by your shadow, and won't reflect any direct sunlight.
If you position yourself so that you're in both direct sunlight and whatever fraction of sunlight the window reflects, you'll note a modest increase of insolation. (Note the spelling.)
If you position yourself so that you're shaded from direct sunlight but in whatever fraction of sunlight the window reflects, you'll note some insolation, but necessarily LESS than from direct sunlight.
If a LOT of windows are reflecting sunlight to the SAME area . . . that's a solar concentrator. Don't stand there.