Chaining with smartcrop imagefield_focus effects does not work

I'm not sure whether this is a bug or support request, so I'm tagging as the latter.

I like to use smartcrop, usually with imagefield_focus in my projects, to give some control to users when they upload images that need to be cropped.

I thought I would be able to chain these effects with a retinafy effect, eg:

1. smart crop to 600x400
2. scale to 300 x 200 with retanify

I would expect the chain of effects above to produce a 600x400 image, 'retinafied' ie scaled in the browser to 300x200. But it doesn't - it produces a 600x400 image displayed at 600x400 in the browser:

<img typeof="foaf:Image" src="http://2ch.local/sites/www.2ch.com/files/styles/article-articlepage-300/public/field/image/201305/mancini.jpeg?itok=2c7wuUg2" alt="" title="">

Am I doing something wrong? Is this a bug in retina_images, or elsewhere?

Thanks!