I did say it's "arguably" second-gen

Your argument is valid, of course. On the flip side, I can say it's "second-gen" in that they made numerous exterior hardware changes: power switch, reset button, rubber bumper pads and placement, SD Card slot cover, camera placement, optical mouse, speaker quality, better e-ink screen (16 shades of gray), all of which are improvements over the EE and address things learned from the usage of the EE by themselves and by customers. Note that the reset button, optical mouse, speaker quality and new e-Ink screen *are* very much new features.

The battery change was specifically to maximize the battery size within the molding of the case. Since the PE is already smaller than the EE's removable battery, making the PE battery removable would have further shrunk the battery capacity (and correspondingly the battery life). Perhaps it's a judgement call whether people would prefer swapping the battery 2-3 times a day versus charging only once.