If a passenger has to board this Augmented Coach, then he has to see the coach display, which shows SExt-1. So, if SE1 is updated, then he might not be able to board the coach. Simple as that. Even in Mumbai Mail (via Allahabad), the Augmented Coach is marked as BEx-1, in Coalfield Express & Co. RSA as DX1. So, better to update what is displayed.