No, not at all. I pay taxes in both states, IL and WI. Were I to take a client to NY for a day, I'd owe state income tax for that day.
You might recall a minor Al Franken scandal, minor cause anyone familiar with him knows he's stupid. He didn't pay taxes in numerous states where he performed, he blamed it on his accountant who must be less than smart. Unless his client, Al, didn't bring it up.
In many states, you earn income there, you pay taxes there. Entertainers and athletes know this well. If the WI Senators are working in IL, they owe taxes. What I don't know is if IL enforces this on entertainers, athletes, et al. If they don't, they should.
But this isn't breaking new ground at all.
I have no knowledge of a situation where employees of a specific state have paid state income taxes in another state on their state income. (Of course, state employees might earn ancillary income elsewhere and be thereby subject to income taxation in other states.)