Daas Yochid: It is a big sugya in Hilchos Shabbos regarding killing lice. The Pachad Yitzchok, not Rav Hutner, explains that while Chazal were aware that there is NO spontaneous generation they described things the way they appear to the naked eye and he says the Halacha follows the appearance. Therefore even though we know today that lice DO come from eggs, they are still mutar to kill on Shabbos because the microscopic eggs are Halachically insignificant. Rav Belsky is clearly following this derech and therefore he is NOT contradicting the Rishonim at all. Additionally based on the life cycle of the anisakis worm, they never exist independently after they are visible, they are in shrimp then smaller fisha nd then larger ones, and there are grounds to say that they are never shoretz al ha’aretz from when they are Halachically significant. Rav Falk uses this sevara in his heter, and Rav Vozner dismisses it in his teshuva, all written well over a decade ago.
I personally think Rav Belsky and Rav Falk’s logic is more compelling, and while I agree with much of what you have written, I must strongly object to any derogatory statements about Rav Belsky.
My issue is that the Gedolei HaPoskim do NOT consider the heter, however logical it seems to me, to be reliable enough to be matir an issur d’Oraisa. I defer to their judgement.