I'm not saying you're wrong, but this isn't obviously correct to me.
Since solar going to a grid is completely dependent upon electronic DC->AC conversion, I would expect that it could follow a lot greater frequency deviation for a lot longer than a mechanical system that will literally rip itself apart on desync.
The real reason that small scale solar PV is grid following (i.e. it depends on an external voltage and frequency reference) is that this ensures power line safety during a power outage. That's it.
An inverter can be programmed to start in the absence of an external reference and it can operate at a wide range of frequencies.
However, DC-AC converters don't have an inherent inertia. They can follow almost any frequency and phase within reason. Certainly a DC-AC converter should be able to respond way faster than any frequency/phase changes that a mechanical system can generate.
In theory, they should be able to set themselves to be ever so slightly closer to ideal so that the amount of power they have to sink is limited but are still exerting a very slight force to bring the grid back into compliance rather than continuing to add load which propagates the collapse.
Low Grid frequency & voltage can cause an increase in current & heating of transmission lines and conductors and can damage the expensive things, this is why these systems trip out automatically at low frequency or low voltage, and why load shedding is necessary