is bitsp cse and adv rank a correlation or a causation?

hey guys, im a 27tard and i have been preparing at mains level only and my mocks are averaging at around 210. i had not really considered bitsat and im pretty unaware about it. (i only watched 1 yt vid explaining what this exam is and also got to know about top 500)
i think it is too late for me to start adv prep rn because i want cse only.
do u think that adv prep is necessary for a top bitsat score (top 500 possibly?) or is mains grind + bitsat mocks okay?

(i would appreciate no trolls)