How to get 'outer' composition's current time?
If you change the inner text layer's source text to this it will work:

thisCompLayer = comp("outer").layer(thisComp.name);    
thisCompLayer.time + thisCompLayer.startTime


You just offset the time to cope with the later start time. 

Looks like when AE calculates values from another composition it just calculates them for the current comp's time. It makes sense, because there could be multiple copies, or no copies at all of the inner comp in the outer comp.