Ah, I can see how it wouldn’t be clear if you weren’t already familiar with it as bicyclist/motorcyclist slang. It is a thing, though; I didn’t make it up.

I should also note that I’m perhaps using it in a particularly derogatory way in this instance. As the first two Urban Dictionary definitions note, sometimes it’s about how how drivers don’t see cyclists because the bars of their cage (their car’s A-pillars) get in the way, or how cars get trapped in traffic in a way that bikes and motorcycles do not (because motorcycles can split lanes, bikes can ride on the shoulder or along paths, etc.).