No, AFAIU the computation is serialized, driven by the microcode and this gate is reused for every step
...but that's exactly the claim, restated.
Not really. It's completely trivial, if extremely slow (which the article acknowledges) to emulate an ALU in software, with access to a single, universal hardware gate. Why don't they just say "we put a NOR gate on a chip, then added all this other stuff (RAM, boot EEPROM, etc.) to make it function as a computer." That would, at least, be a non-misleading statement of the claim.
Yes, it's a "Single board computer with 20 ICs, and a single-gate ALU".
To me it's not really an ALU either, since the NOR gate doesn't really do the job I expect from an ALU.
That’s how I interpreted the OP though... I really don’t know what you were reading into it.