sigh.... you do have a fixed way of thinking...
so the bottom line is
1) the graphics is displayed on screen, pixelated, agreed?
2) extra time is needed to make it look better, agreed?
3) the processor, being Duo core and Quad core, is not at 100% of processor load most of the time. And browsers can actually detect whether it is busy before it make the graphics look better.
whatever you call it, resizing or not, you still do it. Really, you don't need to save the file to call it "resizing". Just the fact that you are sampling the image in a very coarse way and then display it on the screen at a different size, that is resizing already. Tell me, you have an image of 300 x 200. Now you sample the image's pixels and then display it on the screen at 100 x 67, by painting pixel by pixel. (you do still have to paint the pixels, don't you?) the act of painting the pixel different from the original size, is resizing, right on the screen canvas.