Actually it is two piece but it is NOT the same as the old one...at least mine on my PP car is not. Mine has a large rubber donut for the first joint at the back of the transmission than a shaft and a bearing. Then after the middle bearing they have a universal joint instead of the constant velocity joint they had on the s197, and at the differential they have a CV joint.
The two piece shaft is a safety item. It allows the engine to go under the car in a sever front collision rather than into the passenger compartment.
2010 GTRR in 5.0 Magazine [http://www.mustangandfords.com/featured-vehicles/m5lp-1212-2010-ford-mustang-gt-rr-total-fabrication/viewall.html]
2015 White SC, PP, etc....