yes, my two friends both left Taiwan around 12-14 years of age. both know how to speak Mandarin and read some.. not much.
I have no idea how they linked their US passport to their ROC citizenship status.
point being, they did, and was detained. but this was back in 1999.
recently, I have not heard any of my friends having issue. but most all recommend letting the Taiwanese government know my status instead of lying to them and cheating your way in/out hoping you won't get caught.
apparently "oversea chinese" status stamp automatic link your roc passport and your us passport, and is a way of you letting the government know that you have a life else where and asking permission first to come in and out then just simply travel with your us passport.