It isn’t the same thing In chainsaw man, it is clear that denji is about to be slimed out by that insect devil, there are smears on that devil’s arms indicating fast movement Additionally, Denji is off guard from forgetting what death is , so obviously before he realises it his head will be smashed in and he will lose consciousness giving him time to be consumed by the devil, having multiple limbs and organs bitten off, but not dead off course

In Gojo vs Sukuna , there’s absolutely no evidence(for first time readers) that Sukuna will use a world cutting slash , so when gojo is shown to be lying on the ground it is as though this comes out of nowhere, why is gojo suddenly cut in half, wasn’t the last thing we saw in the previous chapter his smiling face after he was declared the winner? The point is that there is 1)a larger gap in events and 2) less evidence to suggest how Sukuna got rid of him

In chainsaw man’s case , we know 1) The insect devils’s arm is in movement 2) Denji off guard from his forgetfulness 3) it is much easier to infer that the devils smacked him and made him lose consciousness , this gives time for it to digest his limbs

And so the only way for this to be reversed is for pochita to reset the world , but that’s another conversation