JPEG quality not applied to PNGs which end up saved as JPGs

I have an image style called "medium" (configurable at /admin/config/media/image-styles/manage/medium) which contains a "Convert" effect as a last step, converting the image to JPG. So, for input /sites/default/files/images/foo.png I get a medium thumbnail at /sites/default/styles/medium/public/images/foo.png.jpg.

At /admin/config/media/image-toolkit I've selected the Imagick toolkit.

The problem is that the JPEG quality configured is not applied for PNG images which end up as JPG as explained above. It's only being applied to JPG source images.

One of the reasons may relate to the fact that ImagickToolkit.php on line 203 checks for $image_format but it should check the resulting image format which can be found at $destination:

    // Only compress JPEG files because other filetypes will increase in filesize
    if (isset($image_format) && in_array($image_format, ['JPEG', 'JPG', 'JPE'])) {