All battery powered devices have vampire drain.
Not sure why your buddy is shocked. Hasn't he ever owned literally anything with batteries before?
Li-Ion batteries typically have a discharge rate of 1.5-5% a month depending on the temp where the battery is stored. These bikes are draining 1-2% a day on a shop floor at room temp, definitely something wrong there.
Just for some context, I charged my spare battery to 50% 5 months ago and haven’t touched it since. I put it in my bike today and it was at 43%.