I expected decent compression, since you said it starts and runs ok. But, extra oil in the cylinder will raise the compression number.
Not too many places the oil can come from. Past the rings, through the valve seals, and that's about all considering how well it runs. The head was just looked at, but maybe the valve seals weren't? Normally with bad seals, the smoke would be worse during high vacuum, as with decelerating.
I've seen Hondas run for months like that with worn rings, then the piston rocks sideways enough for the skirt to rub the cylinder wall, then it will seize. A 200x comes to mind. Or, the rider forgets to top off the oil and the bottom-end goes.