Originally Posted by whitehat
According to GSMArena
the Sony Xperia Z1S will come with bootloader unlocking disabled. (posted 18 Jan 2014) This apparently was requested by T-Mobile.
Please don't shoot the messenger!
Just when T-Mobile is gaining some momentum, they decide to go all corporate.
Maybe that will change after release. I think some HTC phones have to wait awhile after release to get on the unlock list. Maybe this will be similar.