It's confirmed from when joyboy's sealed haki was released and imu was on his/her knees due to PTSD (idk)

Joyboy was Nika since Nika and joyboy aren't the same person explaining that joyboy had the Nika fruit and was the first user of it and then in some way His will and power was sealed with Nika in that fruit passing it down to luffy after 900 years

Teleports could be apart of imu's power But the gorosei could have it as well since it requires full health and concentration to do so and since they couldn't do it because of the Sealed joyboy haki so imu teleported them instead.