Share your experience!
Xperia SP should have Stamina mode and not extended standby so that sounds very strange. What options do you see if you go to Settings -> Power management?
Are you talking about the list of apps under Settings -> Apps -> All?
What happens if you enable Stamina under Settings -> Power management? Do you have any problem using it? You can test if it works by turning off the display, wait 15 minutes and then send an email or a message on Hangouts to the phone.
That's very strange. Could you please check the list of apps again when the phone is set to English (United Kingdom) under Settings -> Language & Input -> Language.
I checked this as I was curious..
I'm running 4.3 in UK language, in Apps > All, mine shows as Eco mode controller (324KB)
Mine is 324 too
So you clear cache and data..force stop and reboot your phone
But after for some time standby time that showed in battery usage page may inaccurate