A great testimonial is all about the transformation that someone experienced while working with you. (We already assume that you’re great to work with and that they were happy about the outcome!) What changed for them? How did their experience feel with you? What was the outcome?
so it never hurts to share a bit about yourself again.
What does someone need/want to know about you? This is a great place to add in a high-level bio and/or show off a bit more of your personality and credibility.