- removable batteries can be stolen,
- can have issues due to bad weather.
They consider their design safer on those two points. It's imho a mistake.
There are many companies producing electric bikes right now: I prefer to see a company that tries to do something different targeting a smaller market segments than seeing the same kind of one-size-fits-all model across multiple brands.
When purchasing an e-bike a removable battery was a must have. The one I wound up purchasing has a pretty heavy duty locking mechanism for the battery so I never really have to worry about it being stolen.