Exactly. The main application of a transfer switch is that it is not going to cause your genset to backfeed into the grid. But for many solar installations that's exactly what you want anyway, so the disconnect logic for an islanding capable inverter is very much the same as for one that is exclusively grid connected, the big difference is that the islanding one will happily generate it's own phase clock if the grid is not present, but for that to work it has to keep its own system running and connected to the house distribution panel while the grid connection is down.
This is much easier to do if it is all integrated into the inverter itself, but that makes for an awkward bunch of wiring, because the inverters are typically not situated right next to the entry point for the grid connection. I'd have to rewire my distribution hookup completely for that kind of functionality, or to have a remote controlled disconnect while the inverter keeps feeding the distribution panel.
A transfer switch is much more applicable to emergency power or ship/shore power situations where you only use one power source at the time. For solar it is normally all on or all off or solar+battery(+wind) on all the time and backfeeding into the grid when it is available and grid power when solar+wind+battery are not available.
This can get complex in a hurry, fortunately there are a number of companies that make excellent components for these applications that you can just order and hook up and call it a day, without ever having to worry if your fancy setup has the right break-before-make order and whether or not it is code compliant. And they're not expensive compared to the rest of the gear you'll need.
