No idea? I just know that it solved the problems “back in the day” in Cubase 7.0.2 etc… 
I’m sure MIXER 1 work fine now with 7.0.6 and 7.5 but I just continue use MIXER 2 because of this.
I have ZERO problems!
If you encounter problems with the mixer… try my work around.
Best Regards
Freddie