X descriptor doesn’t get corrected for too small images

[ausi]

// 1500x1500 large image
$image = new Image('/path/to/image.jpg', $imagine);

$config = (new PictureConfiguration())
    ->setSize((new PictureConfigurationItem())
        ->setResizeConfig((new ResizeConfiguration())
            ->setWidth(1000)
        )
        ->setDensities('1x, 2x')
    )
;

$pictureGenerator->generate($image, $config, new ResizeOptions())->getImg('/path/to')['srcset'];
// cache/dir/4/image-de332f09.jpg 1x, image.jpg 2x

The descriptor for the image.jpg should be 1.5x in this case, because the image didn’t get upscaled and is only 1500 pixels wide instead of the intended 2000.