I suppose some current could flow PV cell --> PV frame --> ground mount --> earth --> AC ground rod --> AC ground wire --> inverter chassis.
But with dirt & ground rod resistance 25 ohms, not much compared to copper ground wire path.
In circuits, there can be shared "ground" or return path, e.g. if analog and digital circuits use same wire to carry power from negative side of supply and reference between chips. Digital usually doesn't care, but analog don't want digital switching currents to cause voltage offset between two devices like sensor and amplifier or ADC.
Similar idea for safety grounds. If an AC circuit shorts and carries 1000A or a few milliseconds, would rather that didn't run through a wire between say SCC and inverter. If PV wire ground and carries 10A (from a 400VDC PV array) continuously (breakers don't trip), I don't want that 10A running through ground wire from main breaker panel --> ground wire --> sub panel --> inverter.
So I would bond main panel, sub panel, outlets, AC ground rod all together with wire.
I would bond DC PV frames, SCC, inverter, possibly battery negative all together.
I would then run a wire between DC ground and AC ground, or rely on inverter chassis as the connection.
As I said earlier, a DC PV fault could deliver Isc continuously through the ground path. If that included AC ground wires (because it went direct to ground rod from PV array), and someone working on AC with all AC sources turned off happened to disconnect ground wire, he could get Voc about 400V to 600VDC.
I don't know what or if code says about this, but I wouldn't rely on code alone if I can think of a fault condition.
If system has isolation switch for both poles PV+/PV- to array, that should interrupt the fault current. But a guy working on AC would have no idea there was an issue.
One I've thought a bit about is battery grounds. SMA Sunny Island doesn't care, isolated or battery negative ground or battery positive ground.
NEC says ground the 48V or greater battery bank.
I have four inverters, one battery string. So I think I need battery negative routed to all inverter chassis, either one daisy chain wire sufficient for catastrophic fuse(s) at battery, or four wires fanning out, sized for breaker in inverter.