Not all fpgu are equal. Maybe this targets those with lower specs.
However I repeat what I said above: hobbyists are free to design their own instruction sets, and good on them!
[0] https://github.com/cliffordwolf/picorv32
[1] https://rwmj.wordpress.com/2018/03/17/playing-with-picorv32-... https://rwmj.wordpress.com/2018/03/18/playing-with-picorv32-...
> ARM paid millions to Hitachi to use SuperH patents in Thumb instruction set
That said: there are a bunch of SOC construction tools for it, so that's definitely a redeeming factor.