The idea behind the serial port on the Surf Squirrel is that it's faster than the Amiga's built-in serial port. Important back in the days of dialup and modems, but not so important now.
Most games playable over serial are probably hardwired to the built-in port, so the Squirrel wouldn't work for them. If they do actually allow you to select which device to use, then, yes, you could use the Squirrel, but it wouldn't make much of a difference over the built-in port.
