You made up an inconsistency. Because there is none.
If Imu wanted to erase O'Hara from the world he would have used his weapon but instead the Gorosei were the ones that decided this and used the event as example to the world.
The Demons of O'Hara are known throughout the entire world of One Piece.
- Imu didn't order the Buster Call on O'Hara, hell Gorosei didn't even want to kill it's citizens (this was Akainu's decision)
- IF Imu wanted to erase O'Hara from history he would have done which he clearly didn't which is why it wasn't nuked.
- The Gorosei Buster Called O'Hara to make an example that if you sneak your nose under the wrong piece of information you will receive heavenly hell for it.
- The Gorosei are actively working on erasing Lulusia existence from the world hence they are clearly hiding that they hold such destructive power.
If Imu wanted to erase O'Hara from the world he would have used his weapon but instead the Gorosei were the ones that decided this and used the event as example to the world.
The Demons of O'Hara are known throughout the entire world of One Piece.
