I can confirm this method is working for Xperia S
. Used @DevShaft
Backup-TA Tool v8.6
I successfully made a backup, unlocked my bootloader this monday (may 27th), restored my bootloader today and now is showing "Bootloader unlock allowed: Yes", tested music info download and is working also.
Also I discovered two things:
There is no need to backup and restore using the same FW (my backup was made with 6.1.A.2.55_1257-6921 and restored with 6.2.B.0.200_1257-4001).
TA backup / restore is working for root while unlocked BL and keep rooted while locked BL.