If you put that cable inside the chainstay, it is very difficult to remove the rear wheel without taking off the BB cover, or whatever system they have for removing the battery.
There's also a speed sensor in the cassette lockring (HG freehubs only for now), so there'll be another cable running along or inside the DS chainstay.
For sure there are better ways, but they generally require complicated routing, or drilling big holes in the chainstay to fit that plug through. For a bike at that price point it would be difficult to achieve.
If you put that cable inside the chainstay, it is very difficult to remove the rear wheel without taking off the BB cover, or whatever system they have for removing the battery.
There's also a speed sensor in the cassette lockring (HG freehubs only for now), so there'll be another cable running along or inside the DS chainstay.