[lmz]

Maybe the "cpu host" is faster and you run a computationally heavy command there, or it's closer to some resource (e.g. you wrote a script to search for some data inside S3 and want to run it on an EC2 instance). Maybe it's something with specialized hardware that you'd like to control (I see /dev is not forwarded).

[amelius]

Isn't it dangerous to use a /dev and /etc from two different systems at the same time?

[lmz]

Yes, if you plan to run disk management commands. Otherwise I don't see what commands would access machine specific device files on a regular basis anyway.