the reason is that in for-loop the rotations add up during the run

whereas in the first example with if, the loop is done through draw() (which loops automatically) and draw() resets the matrix (the rotations) at each new beginning

you can of course fix that in the for loop:

1. // with FOR
2.   translate(width/2, height/2);
3.   for (int i=0; i < 180; i+=1) {
4.     pushMatrix();
5.     rotate(radians(i));
6.     ellipse(0, 0, 350, 120);
7.     popMatrix();
8.   }

this isolates the rotations from each other, so they don't add up but each starts anew.

(Put more precise you save the matrix before the rotation and restore it after the rotation so the next rotation starts with 0 rotation.)

thanks man!!! you're right.

Great!