Been away and busy, sorry for the neglect.
Just a thought - I like to think of Kuen practice (or kata, form, etc) as 'ritualized combat' - sort of an 'in the perfect world' situation.
Then there are drills, exercises to bring the Kuen to life - add some resistance, timing, etc. to the practices.
TFT style practicing also brings this 'flow', this 'life', to the Kuen.
Together with bag work, conditioning, and even, yes, sparring, it starts to develop the martial artist to handle real world situations. I don't feel you can do any of these practices in isolation. There is a time and place for partner work, and a time and place for solo work.