I'm not sure that's the point of the story, but I may be wrong. What I got from it is that the Democratic party has already gerrimanderd basically everywhere they could, leaving few other places to manipulate to counter the Republican effort in Texas (and other states).
I voted, and not for Trump, but I think it's fair to say that both major parties screw around with districting to enhance their advantage and cement their control over states. It just so happens that the Dems have fewer cards to play in this particularly stupid game.
The apocryphal story is actually kind of interesting.
Roads and right of way established during the pre-firearm era were that you'd ride on the left, with people going the opposite way on your right. This was so you could use your dominant hand (usually your right) to use a sword to defend yourself.
Roads after firearms were available often established right of way with riding on the right, with oncoming traffic on the left. This is because when you shoulder a firearm on your right shoulder it's easier to aim left.
Stagecoach drivers would sit in the left seat, with the extra person sitting on the right, holding a shotgun, hence the colloquial term for the front passenger seat.
I have no idea how true this is, but it makes for an interesting story.