I don't know for sure, but I'm not sure you actually 'need' to have any specific training to do walk talks here in the UK, but if your T feels he would need to conduct some personal development in order to be able to provide this as a service, I think that's testament to his desire to do the right thing. I think it's commendable, despite being a real pain for you in the short term. I have done a couple of walk talk sessions with my Ex T, and I know it's something she did more of towards the end of our work, and it is very different. There is a lot more for a T to think about, in my opinion, than just going out for a walk, and I think they should understand all of the complexities that surround it. Maybe he only feels he can do this after taking a course, somewhere he can ask questions of others and talk scenarios through.