I am intested in this question so I made an example.
According to the document, 'The initial condition x0 port accepts nonvirtual bus signals.'
So I made it a nonvirtual bus but there is still a model error at the Bus Selector block.
The error disappeared only after I made the data input u also a nonvirtual bus.
Thus it seems that if you want to utilize "input port" to do initilization of a bus, then the bus input also needs to be a nonvirtual bus. I think this makes sense. Please contact tech support to confirm this.
To make a nonvirtual bus, basically you need to create a Simulink.Bus object and then specify the data type as this bus object. The bus signal line displayed below is nonvirtual bus.
