Yes, that is plausible indeed, but the problem is that there are many explanations which are plausible, but there doesn't seem to be a smoking gun.

Strange about that explanation for example is that the time correlation is backwards. First the solar generation started to drop out and only then central generator stations tripped. Also the on-going frequency oscillations had already stabilized. If it was related to frequency issues, the solar inverters would either have shut down 15 minutes earlier (while the frequency oscillations were at the peak) OR 1-2 minutes later (when power stations tripped and frequency would have dipped)