This is a tangent, but he not only does it by lice, he does it by anisakis. He thinks Chaza”l were wrong, but the Halacha remains. It’s ridiculous to think that Chaza”l would want us to eat sherotzim or do melachah on Shabbos based on their scientific error.
The only classic source (AFAIK) for the possible chashash that Chaza”l were merely basing their observations on contempirary scientists was the Pachad Yitzchak, and he was therefore choshesh for issue.
BTW, the Orchos Shabbos quotes R’ Shlomo Zalman as being mattir killing kinim, which is why I am highly skeptical of the claim that he held like the PY.