Ummm, that's wrong and just plain dumb. If you are legally authorized to make a citizen's arrest (which usually means you have either witnessed a felony or witnessed a "breach of the peace") you are authorized to arrest them. Restraining them, either with commands at gunpoint or with cuffs, is the "arrest" part of citizen's arrest.and unless you are very certain about your ability to make a citizens arrest (which usually does not allow restraint or holding someone at gunpoint)
That being said, it takes a bit of training to properly use handcuffs and no untrained person should consider it. If you've been trained as a LEO or military type, you'd already know the answers to these questions. In other words, if you have to ask, forget the handcuffs or flexicuffs.