In what way does that business model rely on copyright protection? "Get the next chapter early" requires a source of chapters, so all you need is for paying clients to not be motivated to redistribute the chapters in an organised way, or would-be paying clients to not be motivated to use such organised "slightly more chapters of that webnovel you follow" services instead. Humans aren't amoral ideal rational economic actors.

The authors I'm aware of making >$20k don't do any significant gating. That practice is only really common with people republishing through Amazon (which probably demands it).