Greetings!
This is design related query and is not specific to vSAN functionality. As far as vSAN Stretched Cluster is concerned, your VMs will boot on Site-B hosts. The point here is if you don't have 192.168.0.1/24 network on Site-B then VMs will not be accessible which means there will be a DU situation as the workloads running on those VMs will not make any sense as they are not accessible over the network.
You need to take care of the network design part so that VMs are accessible in both the cases (running on Site-A and running on Site-B)
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Cheers!
-Shivam