That's what the solar company told me.
Thanks anyway.
I was thinking about it just then and I think Net Metering solves this.
Even if my solar is generating say 2Kw/h per phase. Total 6kw/h.
And a Heatpump is drawing say 4 kw/h and it is only attached to Phase 1. Essentially, on Phase 1 it is taking 2kW/h from my Solar and 2kW/h from the grid.
But because the other 2 phases, assuming nothing else is drawing any power of note, is generating 2kw/h each and sending it to the grid, my Net is 6-4 = 2 kw/h so the electricity company is netting it off and saying I am selling 2kw/h to them.
I think that's the answer.