Yes, the flat bench could cause shoulder impingement due to locking players/person into a specific position because of the bar. Dumbbells allow true range of nature motion.
Wrong. Only improper technique on the flat bench could cause shoulder impingement. Properly performed, there is no risk of impingement. The standing overhead press has even higher risk of impingement if improperly performed, but zero risk if done correctly. Should we also not do that lift, which is the single most effective upper body lift?