It had nothing to do with security - it had to do with contractual obligations. Contracts with Apple (also Google, Samsung, Mastercard and Visa) required the product to be kept absolutely secret before the public launch. I was a tech lead with developers working on Bank of America’s ATM client - which had firmware and software updates ahead of launch - and I found out about Apple Pay the day it launched. Across the aisle were developers who supported the debit auth platform and they had no idea either.