When you design a new device from the ground up you make them fit in a way that allows the remaining space to be a single large rectangle to be entirely filled with battery. This might require custom PCB to have some L shapes. If you want to target a specific weight and having that much battery is too heavy then you make the device thinner. Instead it looks like they took pre-existing components from other devices such as Pixel phones or the Google Home and put them in a larger case.
It’s not necessarily a problem that this device exists how it is, but that it is a cheap way to go about it and yet still sold at a premium price.
What’s mildy infuriating is your attempt to advertise your app here. I have ad blockers, but I kind of suspect this site has ads on it somewhere.