This is NOT a bug!
If you want to see Your gifs converted, You have to change the extension OR force the creator using the prefs.
Indeed if You do neither specify Creator nor change extension, OSX has no chance to understand is a Gif instead of Jpeg.
There are TWO ways:
a) Use the prefs to replace ".gif" to ".jpg":
in this way OSX can understand is a Jpeg.
Force Creator to Photoshop, for example. In this way it will launch photoshop regardless of extension.
to do this, click on "Like This" and chhose a jpeg made with Photoshop / or Preview.