Board Thread:Manga/@comment-38849221-20190321163015/@comment-37493549-20191007010208

Trums21 wrote: TKGriffiths wrote: It seems like a plot hole for now. Zeke implied something bad would happen if they touched, that's all we know.

Also I think Eren can't simply touch a person with royal blood to trigger the founding titan, they have to be in titan form. Otherwise he could just do it with Historia. Zeke transforming into his titan would give away their position. WRONG. Even in his human form, Eren was still able to use the power of the Founding Titan when he punched or touched the hand of Dina Yeager (in her titan form as the Smiling Titan). You didn't even read what I said lol. I said that ZEKE might have to be in titan form, not Eren. Obviously Eren doesn't have to be in titan form because A) he wasn't the first time he used the founder and B) we know the founding titan's powers can be used while the holder is in human form, Frieda did this to erase Historia's memories.

As it turns out in chapter 221, we now know that neither Eren nor Zeke had to be in titan form to trigger the founder. Zeke being a titan shifter in his human form was enough. But it wouldn't work if he wasn't a titan shifter.

As it turns out in chapter 221 just touching Zeke's human form also worked so that theory was wrong anyway