The line is 213 Vrms phase to Neutral, yes. But for an inverter what we're looking for the line to line, which is 415V, which of course, was proven.
By the way, was reading one phase with the wrong polarity, looks much better now:
Almost feel tempted to just feed the induction motor with this, in fact it's funny that I just happen to do that last week:
The results weren't that bad considering it was just a square wave!
File attached, if someone wants to see what I've done