I have my fathers paddle. He used it from the mid 60's on. When he took his 20 footer out on the St. Lawrence, this was what he used. When he and I paddled Moosehead and elsewhere, this was his paddle. Presumably he learned to like a long paddle to navigate large canoes from his days guiding on Moosehead and the Penobscot. I don't know what he used while he was stocking fires towers for the Maine Forest Service.
The thing that has always stood out to me about his paddle is not the width. The blade is not unusual. What stands out is how long it is. I have tried using it from time to time and I simply can't adjust to it. He was able to use the paddle comfortably either kneeling, sitting or standing. Obviously, it is a stern paddle.
I used to use a wider Old Town paddle. I think it might have been the only wide one in the Old Town shop when I bought it. They were not very popular. I have since switched to a different style of paddle that gives me all of the advantage I need to steer a large canoe without killing my shoulders with extreme resistance.
I agree that this is a custom paddle, but not that it is a "guide" paddle. Guides (as we all should) will try to moderate their effort. Someone using an 11 1/5 inch paddle is either built like hulk hogan, or someone who is not a particularly skilled stern paddler, in my opinion.