Why Does The Retina / Hidpi Add-On Convert To Png And Increases File Size?

I convert detailed images losslessly to jpegs before uploading.

Even at 250kb (2000px max longest edge) the images look very good.

Now, when the HiDPI add-on is activated the resulting png image is reduced to 1000px (longest edge) and the filesize increases to 655kb, i.e. nearly three times as big.

Is there any way we can keep the images as jpg instead?