From look at the board, basically it looks like they did the “hardware” emu approach. But people I know that enjoy retro stuff they either want the look(original or replica case/keyboard, but internal is more modern that runs software emu) or they want the antique(functional original). It’s pretty rare to see these kinda of hardware emu where they bundle chips as close to old ones while trying to replicate how the old hardware work and then drive with another modern board for the input/output.
Sounds a bit like a repogrammable ROM (which is no longer ROM in that case, ROM=Read Only Memory). Kinda what FPGA does, if I’m not mistaken (and what you were referring to, right?).
If you take a look at the die you’ll find what is in effect a ROM on board, a look-up table defining what each instruction does. A machine with said capability can change this ROM, and not merely emulate a different instruction set, but be that instruction set.