Your rigs are profitable up to $0.15 per kWh, and the grid is willing to pay $0.25 per kWh.

Would it be a rational economic decision to turn off the rigs and redirect that power to supply the grid?

Yes, yes it would!!

However, this installation is a "pilot" and is also "off-grid", so there's no ability to supply the grid, as far as I could tell. But if this proves that bitcoin mining using solar + battery works well enough to be viable, future expansion could be built where supplying the grid when it is profitable becomes a capability as well.