It is no way bad therapy. Any method that allows you to speak fluently regardless of circumstance is a good method. Speak fluently on your own for long enough and it will become easier to speak fluently when you are not alone. Practising speaking fluently is a great way to build what is essentially muscle memory. If standing in front of a mirror let's you speak fluently then go for it. Why do you say it's bad advice? What do you reccomend when practising in your own? Practise stuttering?