Board Thread:Theories/@comment-32443384-20180201102915/@comment-1327106-20180202032544

When Colt is talking to Zeke, he says "Our comrades who have been given your spinal fluid... are able to turn into Titans by your roar, and they listen to your commands." Colt is not specific whether "your spinal fluid" is conflating Zeke and his Titan form into the same thing, but when he says "your roar" we know that is something done while Zeke is still in human form. It stands to reason that both the roar and the spinal fluid are referring to things that can be taken from or done in his human form.

It's also possible that being of royal blood, there is very little difference between a royal Eldian's spinal fluid and a Titan's, because Colt makes the observation "It's not as though you have royal blood in your veins" when talking about Zeke's abilities. This means that some Eldians are aware on some level that Zeke's abilities should be a royal ability.

What is good about the scream, is that it can be controlled. If you look at chapter 92, that scenario with the Titan air bombardment would not be effective by conventionally injecting people one at a time and throwing them out of the plane. Instead you can get dozens of Titans in an instant, and Zeke is already in position to command all of them.

Also, Titans created by using Zeke's spinal fluid can move at night, which normal Titans cannot, so they're a little extra compared to the regular ones.