Valve takes a 30% cut and makes eye watering profits. I don't feel it's fair to characterize them as a victim for having to put in some effort to mention a basic standard of quality on their platform.
I really want to see how this plays out. The impossibility to identify AI work and thus keep users happy, vs profitability and steam actually trying to make things work.
Valve is a business but they're also a brand. It doesn't help their brand to be bombarded by slop created by a third party. The initial money is a trifle compared to how many refunds they'll have to dish out. It's like a brute force attack, AI is doing it to a lot of industries and fields including mathematics.