render engine performance

It has been reported one benefit of using DL is that the PP2 render engine 
is much faster than the AE 7 render engine, and hence, rendering an AE comp 
on the PP2 timeline runs much faster.  If this is true, why doesn't Adobe 
replace the AE render engine with the PP2 render engine?

Best,
Christopher

> The AE render engine is much more complex that Premier's render engine ...

Then how is it that Premiere is able to render an AE comp when imported on 
the Premiere timeline?

Best,
Christopher

> The AE render engine is much more complex that Premier's render engine ...

Then how is it that Premiere is able to render an AE comp when imported on 
the Premiere timeline?

Best,
Christopher