I have the EZway app and active cellphone number but I agree with you that the system reject anything except Taiwan ID. The seller told me that only Taiwanese ID number is accepted.
You can possibly complain to EZWay about this (ezway@tradevan.com.tw, English is fine).
It’s probably useless in the short term, but they’ve always been pretty responsive with me and AFAIK SF Express is one of the bigger couriers on there so maybe EZWay can give them a push.
I have had 3 items delivered by SF express from sellers on eBay, I don’t have a Taiwanese ID number so maybe this is down to the seller?