From what you've heard? As far as I knew, Valve kicked off that 25% for ugc. The fact they are going back on that when it is more important than ever (arguably) is a damning look at how they've fallen as far as looking out for their communities goes.
I'm talking general terms when it comes to licencing deals for producing content with someone else's IP, this isn't some new and unexplored territory Valve is pioneering, such licencing deals have existed for a long time.
The only thing that's different is that rather than being a team or a major studio making large project with someone else's IP, this is an individual (or two) making bite-sized chunks.
However I agree fully that what they've done here is scummy.