There are some threads about this topic, but are WAY too long. Anyhow, MBL was not going into sleep mode (blue led).
I was able to achieved it by doing the following:
Disable Remote Access (yes, mobile apps will not work)
Harddisk Sleep Enable
And whala! MBL went into sleep mode!
Whether it is a bug or not, who knows. It will all depend on your needs.