Developers reported that the iOS 12.3 EMV Express Transit feature was missing in iOS 12.4 beta 1. The feature is still missing in iOS 12.4 Public Beta 2 (16G5027i), stay away if you use it. Suica Express Transit performance remains stellar and solid as it is in iOS 12.3.
It’s weird the new feature would be missing at this stage in the public beta beta cycle. I guess this means the under the hood Apple Pay Wallet construction that started in iOS 12.2 continues in the run up to Apple Card and iOS 13. I’m sure we’ll hear all about it at WWDC19.