I agree with Apillar. I drove through western Maryland in April 2012, and thought that was the prettiest part of the state.
Anyway, I just checked electoral maps from 2016 and 2020, and in both of those maps, all three of the counties in question voted Republican, while the high populations around Baltimore and DC carried the state for the Democrats. The article doesn’t say it, but maybe the people in those counties want to be in a red state, for a change.
Finally, transferring the three counties to West Virginia would eliminate the peculiar geography around the town of Hancock, where Maryland is only three miles wide. I stayed overnight in Hancock on the trip mentioned above. And near the motel was a Sheetz gas station; that would look better if it was in West Virginia, where so many other things are named after former senator Robert Byrd.
It would keep or flip WV’s two senate seats, for one thing. :^)