Changes in the physical state affected during certain conditions such as trance are recorded. There is nothing fictional or unscientific about the ordeal of the molten metal. Kai-Shiavux had also undergone the test of fire without any harm. As an infant, Asho Zarathushtra successfully prevailed the ordeal of fire, unhurt and uneffected. Ignorance of the scriptures is no reason to let heresy and heretics have their way.
Religion is a matter of faith .
Religion is not theory conceptualised by the imperfectly evolved mind of a philosopher, theologist, heretic reformer or a student of languages. Religion is revealed . It is the proclamation of the result of direct communion of a perfected soul with the Divinity. All religions are manifested on Earth according to the Divine Will, as per Yasna 19, and all teach spirituality. Till Anquetil Duperron came to India in the 18th century, Zarthushti religion was studied and taught by Zarthushtis.