Ok, can you give an example of the RD with short cage and pointing forwards?
Being spring loaded, the derailleurs position is determined by the take up in the chain. In the first photo, the combination is the large chainring with the rear largest cog. So of course the derailleur will be in the forward position. This is also determined by the adjustment of the length of the chain given the cog/crank combinations and length of chainstay i.e. distance from crank spindle to rear axle length.