I'm a little skeptical on the 1-phase versus 3-phase in the manual. The 550 Cl*mer manual says the unloaded ACV at 4000 rpm for the 1-phase is 50VAC, but you already showed us it's closer to the 75VAC they describe for the 3-phase (which is basically what I measured on my 3-phase).
I do recall checking some KZ (650 or 550?) 1-phase and getting about the same as expected in the 3-phase. Not sure why the 1000 would be different if in fact it is.
I find too many errors in the manuals (more so in the Cl*mer, but some in the FSM too) to take what's in print as gospel. That's why it's so enlightening to get actual data like you provided.
As we already know, the unloaded tests are not a great indicator of power output. Inductance is weird like that.