Somewhere in my photography career — and I don’t recall exactly when — I realized that my addiction to bokeh and shallow depth-of-field was doing me no favors. Although I loved the results and, to be honest, I still do, it isn't the only solution for portraits. In fact, there are often times it's not the best solution either.
Getting close to the model with a wide-angle lens can feel strange, for both the model and the photographer, but it can be highly effective in some scenarios. One situation I often reach for the wide-angle is more editorial shots. Not only is it excellent for capturing the interesting surroundings or set (if you have one), but it allows a better view of the details of the subject's outfit too. Sometimes, you simply need to be bold and shy away from the easy shot, which for me is, invariably, a wide-open telephoto lens with no details anywhere but the subject's face.
When do you use a wide-angle lens in portraiture?
It’s a fair, and interesting, question, but your example is flawed. You’re referencing a medium format lens but make no mention of the .79 crop factor, which makes that lens into something more like a 25-50/3.2 in full-frame terms. There’s more “normal” there than “wide-angle.”
Agree that the crop should be accounted for, especially depth of field. But I think 25mm equivalent is pretty dang wide. Even 35mm is considered wide for portraits.