The 13" MBP never had a discrete GPU. It had an nVidia integrated GPU (integrated to the north bridge and sharing system memory).
Err, the Geforce 320M from 2 generations ago was effectively a discreet GPU; the fact that it used shared system RAM rather than dedicated GDDR3-4-5 memory doesn't change that.
It's a separate processor, not one integrated in the north bridge or part of the CPU die; that's what qualifies it as a discreet GPU, not the type of memory it uses.