User blog comment:God of nothing/Titan shifters-Invincible?/@comment-17563801-20131001222038/@comment-179280-20131002044234

But you have to remember that Titan Shifters aren't anything special, besides being able to control their Titan Body and transform at will.

If you remember, Ymir had the exact same appearance in Titan form before AND after becoming a Shifter, not being taller than 4m (13ft). She was not a Titan Shifter before year 845, and she likely gained that ability after eating Berik.