Interacting between Premiere in a non square pixel sequence and an image editing app will cause round to be elipse. The excpetion is in a Photoshop NTSC preset. one can create a round circle, It will appear round in Premiere, export round to an NTSC monitor, but playback elipse on a PC monitor.
Exporting a Bitmap from Premiere, open a new NTSC preset in Photoshop and Place the bitmap into it…elipse!
Previewing NTSC should be done on an NTSC monitor or Premiere’s program window..