I read a lot about the difference between CISC and RISC architectures from different sources. One of the things that seemed to be agreed upon is that CISC is always used with Von Neumann whereas RISC is used with Harvard architecture. But I couldn't quite grasp the reason behind this classification.
There is no relations between Instruction Set (RISC and CISC) with architecture of the processor (Harvard Architecture and Von Neumann Architecture). Both instruction set can be used with any of the architecture.
Older ARM architecture used Von Neumann Architecture with RISC, and later with ARM9 they shifted to Harvard Architecture with RISC. Latest ARM processor uses much more advanced hybrid architecture.