I believe that the 60.5Hz cutoff is a requirement of the UL1741 standard, which I believe is required in all jurisdictions in the US now. So I suppose it doesn’t necessarily apply to all inverters as off grid inverters don’t need to conform to that standard and perhaps other countries have other requirements. But I believe that any grid connected inverter installed within at least the past couple of years will cut off at 60.5Hz. It is possible that I a mistaken about this though.
I decided to reply to this old thread since this information does not appear to be correct. The following is from Enphase ISO-NE 2018 profile:
FREQUENCY LIMITS
Over frequency disconnect Time Magnitude
Limit (fast) 160 ms 62.00 Hz
Limit (slow) 300,000 ms 61.20 Hz
Under frequency disconnect Time Magnitude
Limit (fast) 160 ms 56.50 Hz
Limit (slow) 300,000 ms 58.50 Hz
Reconnect frequency Magnitude
High 61.20 Hz
Low 58.50 Hz
RECONNECT
Start / Reconnect time 300 s
Anti-islanding reconnect time (long) 300 s
RAMP RATES
Soft-start ramp rate 2.00 %/s