This should be fine, I do not see anything in the worker requirements that require the same subnet.
I think the following topic might be relevant. I do not think the broadcast domain is relevant based on how the Tableau Server nodes communicate.
"When a Tableau server that's running the data engine or the repository loses connectivity with the other nodes, it checks with a gateway process external to itself (but still within the Tableau Server cluster) to determine which node failed and whether any standby processes now need to become active."
I suggest testing this to satisfy your curiosity as well. configure the environment, then disconnect the network for each node and see what happens.
Let us know how it goes.