It doesn't seem like it's strictly true that they don't charge trading fees.

From their docs, it looks like they charge fees to bet "takers" (as opposed to makers), but exclude the geopolitical and world-events markets where they don't charge fees.

I have to imagine that may be related to some of the blow-back towards prediction markets about profiting on topics like war & their potential for manipulation.

Given it sounds like the bot bets everywhere other than sports, many of those categories would likely have fees in this case.