You are correct that the CCNA/CCNP racks were created using the hardware we once had in the CCIEv4 racks. However, to clarify:
1. All of the switches in the CCNA/CCNP racks are 3560s.
2. For doing any CCNA/CCNP labs, there is no benefit of using CSRv's versus real routers. The combination of four routers and three switches in each CCNA/CCNP rack (not including the Backbone Router and Frame-Relay switch) are quite sufficient for doing any CCNA/CCNP labs.
As a matter of fact, those are the only racks I use when doing all of my demonstrations during my classes. Even the CCIE-level topics I've taught (such as BGP, complex 802.1s MST labs, and...soon...MPLS) use those racks.
The main benefit of using the CCIE racks are simply for topologies that require more than four routers but considering that each of the three switches can also double as a router you really have up to seven "routers" available to you in those racks.
Hope that helps!