As for Parsi anti-conversion policies: Parsi thinking has absorbed several idea from Hinduism. Reincarnation is one of them (you will never hear Iranian Zoroastrians speak of reincarnation) and another one is the belief in the caste system. Because what the anti-conversion effectively does is that it creates an additional caste within the Hindu caste system, namely a Parsi caste! And like all castes, it sees membership as a matter of birth right only. The idea does not have any other foundation from within Zoroastrianism, not even from the Vendidad. The Iranian Zoroastrians do for example NOT consider themselves an ETHNIC identity but strictly a religious one.
But on the other hand, after a 1,200-year presence in India, should we not really be surprised Parsi belief has not absorbed more Hinduist ideas???