Reading Frank Furedi and Bob Brecher, one might think that a PhD, a smattering of part-time seminar leading, and a publications record qualifies anyone to teach adults. The value of training depends on how teaching is perceived and defined. If it is giving inspirational lectures and seminars then a little charisma may be enough.
But teaching can mean something more imaginative and engaging than that practised in British universities. Academic ability and communications skills (in the didactic context) aren't platonic knowledge, nor are they inevitable correlates. A teaching qualification would therefore seem sensible in addressing the absence in the postgraduate system of opportunities for professional practice.