I do not believe UO would implement a costly, inconvenient, frustrating process (for both guests and employees) unless there was an injury or an in-progress lawsuit. UO doesn’t enjoy making everyone’s life miserable.
Selfie sticks are something that coaster designers could not have predicted back in the late 1990’s when these coasters were built. A collapsible, concealable pole that can be extended during the ride, and that reaches outside the ride envelope, presents a tremendous danger.
I assume this is a stop-gap measure until a lawsuit is settled. Although metal detectors can’t detect ALL selfie sticks, it’s important that UO demonstrates that it is temporarily making a best effort to protect guests during a litigation process until things are settled. I’ve seen similar knee-jerk reactions in the past when “incidents” have occurred (no spinning on MIB! Only 4 people per RV on Ripsaw!).
The above is all conjecture and not based on any insider info.