It’s probably very influenced by the fact that currently popular learning materials feature sitelen pona from the beginning and throughout, while in the past it was an more of an afterthought

Isn't "li" from Tok Pisin "i"?

Thanks for providing some additional context! This chart is rather confusing to me - what does "slow" have in common with "test"?

I don’t intuit the meaning of the diagrams. How are they formed? What do the concentric circles mean? What does the varying darkness indicate? What’s a radix? Thank you!!