Worse case scenario, chance in a million, is that the pole could get jammed between a wheel and the track. This would more likely cause the car to slow or stop, which could still be dangerous, and would be at least a huge inconvenience to hundreds of guests. Witness what a bag did to DCAs Screamin' a few years back.
As big a worry is a flying stick either hitting show scenery, or worse, a rider seated behind. Even at 20mph getting a stick and cellphone - or either item - in the face doesn't bear thinking about.
I'll also add that the reports actually mentioned by the media are just the tip of the iceberg.
There's been many complaints about Universals zero tolerance policy on carry on items on their faster attractions. I'd hate to see this the norm on more attractions but sadly guests more and more need protecting from theirselves.