Default Wifi "always-on" mode won't drain battery?

Has anyone noticed that when you set the Wifi mode to always-on, the battery drains like if the wifi was on "turn off wifi when screen off" mode?

There is a check box in the wifi settings to optimize battery life when using wifi maybe that is the reason?
CURRENT: Lenovo P780 ROM: SLX v.26 MODEM: V15 2013/05/27

PAST: Palm m125, m500, m505, Zire 71, Zire 72, Mio P500, Samsung Omnia II, HTC Wildfire, ZTE Blade, ZTE Grand X In, Samsung Galaxy S2 Plus, Samsung Galaxy Note