I don't have an answer but want to hear what people say...
I asked the salesman while I was there kicking the tires and he told me it wasn't approved by the government. I said, "It seems like the sort of thing diesel truck owners do all the time. They buy a tuner and have the computer dump more fuel."
Neither of us knew what was ok and what wasn't.
I'm not sure how much I care about government approval. If it's the same hardware but detuned on the 3301 I wouldn't feel guilty at all getting the extra HP. I'm probably missing something.
Its nothing new and nothing unique to kubota. Mfgs have been doing it across the board for years.
Sometimes the same engine might span 3 HP ranges. A detuned one, a std one, then one with a turbo.