That’s not what Slifkin says. I’ll let you find it on anisakis, but on the post you referred to, he does not say as R’ Aryeh Carmel quotes R’ Dessler about lice).
When the anisakis issue came up a few years ago, R’ Shmuel Aurbach was quoted as saying his father’s psak l’hatir is not relevant to the metzius as we now know it. If he held like R’ Aryeh Carmel quotes R’ Dessler, the psak could never change.