It's possible that Sukuna knew Gojo would immediately let his guard down if he made the latter believe that he had won their bout. But consider this - the mangaka himself claiming that Gojo died ...

Fans know that in JJK chapter 236, a beloved character, Gojo Satoru, died. In the battle against Sukuna, Gojo fell ... the King of Curses in the very last panel of the chapter.

but we also saw a glimpse of Satoru Gojo in the last panel of the chapter, hinting at his return after he died at the hands of Sukuna in chapter 236. However, there are quite a few theories ...