Where did you find the dyno sheet? I have that one, too, but don't remember where I found it.
I know more about the Yanmar products. Many of their tractor engines are also used in marine applications, generators, and refrigeration units, as well as industrial applications. While many/most parts interchange, the engine model numbers and their power ratings do vary markedly. For instance, the version in my Yanmar tractor of a small 3 cylinder diesel is 18 engine, 15 PTO hp at 2600 RPM in the tractor, but nearly 24 horsepower in industrial applications, at 3600 RPM. In marine applications output varies according to the rated RPM but is generally higher, presumably because of the unlimited cooling capacity. Different casting numbers exist for all these applications even though parts are interchangeable.
It seems like the power curve listed is from a tractor manual, and thus is "as-installed." I would predict Mitsubishi would be similar to Yanmar and have different numbers and outputs if engines in the same family, depending on application.
I'm not sure about the different PTO speeds vs efficiency. I don't think there would be meaningful differences, but I don't have any evidence for that. Gear efficiencies shouldn't change unless there are additional gears within the drive train in different speeds. Otherwise, the power should be the same.