Deriving the correct graphical password pattern (a feature provided by Android) based on screen smudges is quite a bit simpler than deriving the correct PIN from the smudges on a 3x3 number pad. Some studies have had over a 90% success rate.
I don't think this is the type of feature people should be encouraged to use. As it does exist on W8 it stands to reason it will eventually pop up in WP, but personally I think they'd be doing some folks a favour by omitting it.