No they do not train on wild birds. I think there are some regional differences. I am sure where you are, and your experience, a lot of trial guys train on wild birds. I do not believe that is the case for trialers all over the country. I believe in certain areas of the country field trial dogs rarely if ever see a wild bird. In other areas of the country trial dogs see wild birds regularly. I think much of it depends on the wild birds available locally. In areas with prairie or ruffed grouse, wild bird field trials and training are common. Where I live pheasants are the most prevalent wild bird available.
And to be clear, I am not bashing field trial dogs nor am I anti FT. I understand the history of the rift between hunters and field trialers. I own a Pointer and Springer. Both come from field trial lines. My Pointer runs big and I like it for the reasons you point out. I will only buy dogs with out field trial lines, but the dogs must also hunt wild birds regularly.
Maybe I am reading too much into the intent of your post, and if that’s the case, please let me know. You’re tired of hearing hunters bash trial dogs for the reasons you point out. I am too. I am also tired of field trialers’ dismissal of those who do not trial and “only hunt.”