The only feature I care about here, is that it charges over USB-C PD, which every ebike battery for the last 12 years could have done, and should have done, yet here we are.

Is it the very first? I have no idea. But it's the first that I've run across, and I'm ecstatic that it exists.

Proprietary power bricks for anything are stone-age and should be shunned by the market. Maybe the ebike market will start doing so.