Solder Pad and Stencil Mask Data Sheet - Confused
Yes they are rotated. 
The "Stencil Mask" is a physical metal stencil created to be used by the assembly house to print solder paste. The grid reduces the solder coverage to the typical 70% or so for a pad. For example the tab on TO252 package usually is split into 4 or 9 . Also the polarity notch means that a bit less solder is required in that area. If you have too much solder coverage it might short under the device. 


TO-252: 




Not sure why they put the tabs on there, but they are dimensioned so they probably belong. They may be intended to draw out excess solder to prevent shorting. 
The pads represent the copper, the stencil mask defines the holes where the solder paste is printed. They're on different layers in your footprint, and both are necessary (unless you're planning on never making a stencil and always hand soldering). Note that the copper dimensions are larger than the solder paste. 


Note: They don't define the solder mask layer, but you should. In particular, the 'tabs' should probably be free of solder mask (as well as the pads proper, of course). 

Typical stencil: