Have you ever looked at what a string plug looks like inside the tire after you remove it? If done well, with liberal amounts of cement, they bubble up and are the size of a strawberry or so inside the tire. No way that centrifugal force would ever sling one out.
Good ream job and lots of cement!
I've run several tens of thousands of miles on plugged tires and never had a problem, with one exception.
The only plug that ever failed for me, was a mushroom type plug, and it was installed by a guy that sells the kits.
Took it out after 500 miles and replaced it with a string type and then rode the tire until it was completely wasted.
I'd also like to add that I have more faith in these repairs ............. because I have tire pressure monitoring. I'm a big redneck and I've made fun of TPM for years, until it saved my bacon on several occasions.
It let's you closely monitor tire pressures and gives you a " heads up" for anything other than a catastrophic tire failure.