CS: ” I’m saying that just as Shimshon is considered shofet 40 years in Torah, even though he only physically led them for 20, because his influence continued after his passing, so too here”
It does NOT say that he was shofet for 40 years. Rather it says twice that he was shofet 20 years. The Radak discusses this and he is the one who cites a midrash which says that the second time it says it to indicate that the Plishtim were scared of him for twenty years after his petirah.
No one that I have found claims that he was considered a shofet after he was niftar.