I know what you mean. I think this is a great and useful technique.
I sometimes do that on my own. My T does it to an extent - for example, if I'm telling him facts (not really complaining, not happy either, just stating how I did something), he may rephrase it to show what I accomplished and what skills I used. I find it useful too and a good idea. I think that, throughout the years, this has changed my mindset - it helped me to appreciate what used to seem like small things in myself and others. I also use this. Though you have to be willing and prepared to see the good in yourself and even in parts you make think of as unimportant or harmful. (So by the way, great job to you for seeing your ED in that new light!).
There is also something called "positive intention". Every part of you, no matter how self-destructive it may seem,has your best interest in mind. So it's a good shift in perspective to reach that common ground, ask yourself what that part of you (such as an ED or anything, really) wants for you that would be good, so you can look for healthier alternatives of achieving what you need. Is this also something that your T does? Or the same principle?