Good point Rob. Isn't OP after a commuter bike wearing backpack option though, so may be fine for that. It's also stealthier than a frame-mounted battery with empty double panniers covering the battery (for example) - The Bosch battery is only about 2 1/2kg, right ?
For heavy loads on the rear (proper shopping trips !) I personally found it a lot easier on a long wheelbase bike with behind-the-seatpost mounted battery that will take fully loaded side panniers without destabilizing things. Works better as a 'light cargo bike' than a compact hybrid/MTB-type bike. Gave up trying to carry heavy shopping on side panniers on my Trek. It was fine to have weight on the rack itself, but not also with any significant weight in side panniers. Handling affected too much. Perhaps being a 62kg smout doesn't help either !