@CyanHide
Late reply, but this "Formless" is the style of one of Kengan Asura's top fighters and much much later....let's just say it turns out it can be "learned"
https://kenganverse.fandom.com/wiki/Kanoh_Agito
That said being like "water" is also involved, it's to explain the quick switching in fighting styles and movement mid-attack or mid-counterattack
Also, in one of the chapters, "Formless" was directly compared to Systema