I have a query in context to lab-ssh hardening and sudo question 7 The command . . .

SidB:
I have a query in context to lab-ssh hardening and sudo question 7

The command

useradd -s /bin/bash -g admin -d /home/rob

gives incomplete results whereas the below command is correct

usermod -G admin rob

Please can you help me understand the difference? Because on doing

id rob

I get the same output

unnivkn:
https://www.tecmint.com/add-users-in-linux/