I also found Grupo 0 underwhelming.

Firstly as Circusplaza says, they just call 0 and 1 together. Why make a big deal in the announcement "we want you to feel special" and then not implement it properly.

Secondly because group 0 is not automatically extended to the boarding cards of the other passengers on same PNR. You must board as a group and cannot board separately. On one occassion it wasn't clear to the gate assistant in TFS how many people on my ticket. I had to walk back again when last person on my ticket was denied because it says group 3. Having thus learned to wait for all my group, at the next flight in MAD I was told "please walk on, sir" and then difficult to explain succinctly that previous experience warned against it.