Excellent.
Next time you update your maps, select device AND computer, and all will be well.
It makes some sense that BaseCamp will draw compatible maps across from a device, then remove them when the device is disconnected. Several bods have assorted GPS devices for various purposes, each carrying different maps and assorted map versions. Each device can be connected, the map drawn across, a route plotted, the route exported to the device and the device disconnected, all in perfect harmony.