What situations can possibly occur that would require the relay in a hybrid inverter, whose purpose is purely to disconnect the grid in the event of an outage, to pass current while it is disconnecting?
The point about the relay not having to turn off 200A when the grid fails has some merit. By definition, the grid has gone down so it is no longer providing current. However, once you consider all possibilities such as back current from motor loads, I could imagine there could be a reasonable current. My reading of the relay spec sheet tells me that the relay can handle it so it seems like it is covered either way.
There is no scenario where >100A is passing through this inverter and it has a chance of seamlessly transferring.
That is an interesting point. If the load is beyond the capability of the inverter to service, the inverter will have to shut down.
This particular inverter has some impressive RunSurge capability. [14,000W (10 min.), 16,000W (5 min.)] For many households, 16KW is going to be an unusual and momentary event. Consequently, there is a good chance the inverter would ride out the transition. However, if the load is closer to 100A (24KW), it will probably shut down almost instantly.
Edit: Added paragraph space for clarity.
The appeal of this type of system is that there is no separate critical loads box so it is easier to wire up and you can choose what to power during a power outage.... you just can't choose to power everything. The trade-off is that at the time of a power failure, there is a possibility of the inverter shutting down before you can shed enough loads. For many (most?)households this will be a low probability.
I am investigating a similar system right now. I like this trade-off because I don't have to move a whole bunch of circuits to a separate box. Furthermore, my Sense system tells me I rarely have a total load above 16KW. However, I am wondering if I should move one or two circuits (like the oven) to a small grid-only breaker box. This would drastically reduce the possibility of the inverter being overloaded at the moment of grid failure and I would not be running the oven during a grid failure anyway. I hope to someday have an EV and I will almost certainly not run the charger through the inverter.