The 2013 rMBPs last October went with PCI-e SSDs, Thunderbolt 2, 802.11ac wifi, more energy efficient Haswell CPUs and different GPUs. Basically a major refinement of what started with the 2012 rMBPs.
It'll work. Both the mid-2012 and early-2013 models are still considered as 2012 MBPs because they use the Ivy Bridge chipset. And besides both use blade-SATA.
So far, only the late-2013 (Haswell) MBPs use the blade PCIe. Apple switched to PCIe because it's way faster than SATA.