They are talking about moving the existing lewd stuff out onto a new platform, not starting a PornHub alternative. There is obviously enough in it for Amazon, otherwise they would just ban the pools outright.
I understand the distinction, but ultimately the reputation issue for twitch would be identical.
"They're opening a porn site?"
"No no, its a separate site for softcore...err sexually suggestive material"
It isn't a win either way, and they'd be entering established markets that already have entrenched businesses and wouldn't have the 'walk through' traffic the video games sections of twitch provide.