Yes, the TA partition has your UNIQUE DRM info needed for Sony's proprietary software to work. (aka bravia engine and xreality) take note of the word UNIQUE.. you cannot use a TA backup from another phone.. So you really have to back it up.. A few minutes of effort to back it up is worth spending rather than losing your keys forever..
As I've read from one of the posts on other threads, restoring the TA partition would not relock your bootloader.. They are two separate steps.. You have to manually relock it after restoring.. Which as far as i understand is fairly easy although I haven't done it myself..
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