One dimensional personal trainers tend to be very focused at what they are good at but what they are good at may not suit your client and their goals.
Let’s say you’re a personal trainer who’s into bodybuilding and your client wants to be functional, fit and slim, there may be a conflict of interest. (However, all styles of fitness have some benefits to any style of training.)
Whether you’re a bodybuilder or a functional trainer it doesn’t really matter… what does matter is that you know how to give your clients the results they actually want, this comes from constantly improving your own education no matter what style of training you may prefer.
A good coach/personal trainer is a great listener, a great observer and also able to read between the lines and understand what your client is not saying. For example, when you see them move dysfunctionally, look at correcting the movements and notice what else may be weak and where else they are strong. That way you can focus on one of his or her strengths and of his or her weaknesses or imbalances rather than hammering them with something that works for you!