Like I said, grid tied uses the grid as a “battery”. Thats why it shuts off when the grid fails like a battery powered inverter would if the batteries failed.

Panels feeding an inverter without a battery would have voltages all over the map. The battery helps smooth out voltage variances. Like a capacitor.

When a grid tied system loses the grid it shuts down to protect the inverter and not back feed the grid. If there was a battery bank in between the panels and inverter and the inverter had an automatic transfer switching system it would keep power on until the batteries were drained. A larger group of panels would lengthen the battery time.

Its not a legality issue, its a financial one.