User blog comment:Nayuta Ito/faketest/e0/@comment-30754445-20180804174000/@comment-35392788-20180804180833

ψ(Ω2+1) is actually supposed to be ψ(εΩ+1)ω, and I think ψ(Ω2+Ω) would rather be ψ(εΩ+2), but don't quote me on the last one.

Then, he just used psi because it's that common for OCFs. Most things that use UNOCF mention it anyway. Changing it now would cause more problems than it would solve anyway.

Finally, Username created this OCF mainly so that it matched up with UNAN, and it just happened to be a very intuitive OCF for a newbie. And then, I don't think Username is notorious for being good at formalizing things :

UNAN : no complete ruleset past a certain point iirc

UNOCF : not well-defined, but Nish and I are working on that

Pi function : VERY ill-defined