It is essential that people who register with the EUSS receive physical documentation. All other migrants and British citizens can choose to obtain physical documentation to prove their status.  
The Government has denied this right to EU nationals and their families. We know this will lead to discrimination. 
We cannot rely on an untested online database as the only means of evidencing status and rights, and it is disgraceful for the Home Office to use EU citizens in their experiments for a digital immigration system.  
Being allowed to register to obtain physical documentation is not comparable with compulsory national ID cards, and it is dangerous and wrong for ministers to imply this.