I was actually thinking of other non-transit e-money cards like iD and WAON (my fault that wasn't clear from my comment). For an iD card linked to an SMBC credit card, your iD spending limit is the same as your credit limit [1] - which can be upwards of ¥10M. I don't know how or why anybody would spend that much in iD transactions, but I bring it up because it shows that SMBC seemingly has as much trust in iD security as they do for Visa's online transaction processing.

[1] https://qa.smbc-card.com/mem/detail?site=4H4A00IO&category=1...