The code change for this was 2008 NOT 2011
Just for clarification , the rule to have separate neutral and grounds was 2008?
When I wired my house (2005) I did not separate them.
My breaker panel could be considered a sub panel I guess but not sure.
There is a main breaker only in the garage, it then feeds to a closet in the house where the breaker panel is. Sch 40 pvc between the two panels with 4 wire , two hots , neutral and ground wire.
Neutral and ground are not separated .
And if it matters this is all the same structure.