Wolf:
I understand it to mean that Chazal made the wrong Halachic decision. None the less, since Halacha follows Chazal, Teva changes slightly so that the halachic definition of “grows from an egg” can no longer include Lice, and as such they are now correctly excluded. This may also include changing the Halachic definition, but since that is also defined by Chazal, even if they did not mean to change the Halachic definition, none the less it is changed.