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It doesn't quite work that way.

Generally, the power company energizes several conductors with different phase power, AC, then transforms 1 to 3 phases down to a lower voltage for the residential use. The power leaves the transformer and into a panelboard, where it is then fed to numerous circuits for use at the receptacles and a couple of hard wired motors.

Photovoltaics naturally generate DC power, need to be inverted for AC use and if fed back onto a grid, require another transformer and phasing circuitry so it doesn't interfere with the power from elsewhere. An electrical generator as a rotating piece of equipment, naturally generates 3 phases from 3 different tap points. Additional safety circuitry/switching/control would also be required so that where ever a system is de-energized, the lineman repairing the distribution system doesn't get electrocuted/energized from an unknown power source backfeeding his system.

Same reason you don't hook up generator power to a receptacle in the wall to energize your panelboard.

Most metering, (what the power company now uses to measure your KW-hr power consumption) is now digital and not necessarily able to 'roll back'.

IMHO, the most efficient use of PV is on DC or motor loads or to switch to solar heat vice electric heat. Solar for DC loads such as computers might be intelligent. It would be far 'greener' to allow a separate PV DC power source to the PC, than a switching power supply, converting AC to DC.

I haven't run the particular numbers, but generally the industry is tooled up for single and three phase transformers, one per 1 (maybe a handful depending on distance of secondary runs) panelboard, and then simple switching devices. Economies of scale for both installation and maintenance favor that metric. Moving to other system designs might provide some marginal efficiencies, but are likely to be dwarfed by a factor of 2 to orders of magnitude when more sophisticated phasing requirements at different voltages are encountered.

I suspect if they get a check back, it's due to a subsidized effort or policy to promote a more smooth distribution of power demand over the daily demand cycle.

At the individual level, the PV might greatly increase the individual user's ability to remain within the Base Rate power cost, thereby only paying .13-.18 cents /kWhr vice .25 or greater for the whole bill if he happens to exceed a total kWhr use at one point in the month.