I'd love to be able to run my Apple II's at 14 MHz...6502 cpus and support chips are still in production. There are also many, many (open source) FPGA implementations.
Smartykit seems to be a similar project to this Ben Eater 6502 tutorial and kit. I had a lot of fun, and learned a lot about microprocessors, by building the Ben Eater kit.
The Ben Eater kit has the advantage of not using arduino chips for its (admittedly more primitive) I/O.
A Raspberry Pi or Arduino can teach the same and at the end is far more practical and useful. In the case of the RPi, you can even run a modern operating system and software.I think it's meant to be thought of more as an educational tool. Something like this might be good for teaching kids about each of the parts that goes together to form a simple computer, and what each of those components does, for example. A class could then maybe learn a bit of BASIC programming and enter some simple programs in, with an explanation of what each chip is doing in response to each command. Something like a Raspberry Pi might be fine for teaching programming on, and probably a lot more useful as an end-product, but it's a system on a chip with a lot of complex systems obfuscating its operation from the end-user.
On a side note, if you search for SmartyKit on Amazon, you get a bunch of "SmartyKat" cat toys instead. : P