Correction, my bad, the formation I've come across that is illegal is this one:

------ST------
AMC------AMR
---MC--MC---
DML-DMC-DMR
---DC--DC----
-----GK-------

It's the classic "metodo", arguably reinvented in Barcelona, (with the influence of Cruijff' school).
The Question: Are Barcelona reinventing the W-W formation? | Jonathan Wilson | Sport | theguardian.com

It makes your ball possession down to 20% even if you put arrows down. lol