To be clear, I understand the student in question cannot have access to an actual 6502-based machine but a simple 8-bit computer (without a lot of custom chips

To be clear, I understand the student in question cannot have access to an actual 6502-based machine but a simple 8-bit computer (without a lot of custom chips for graphics/sounds/etc) is easily understandable by a reasonably intelligent person and the CPU itself can be expressed in a simple state machine. Given the documentation for a real machine, the student can run by hand the system clock and understand memory latency, the instructions that can be executed, the interrupts, etc. That's a level of fundamental understanding that the vast majority of newly-minted "programmers" have not and will never attain.