Sure, but under the hood both the HTML5 APIs and Pepper APIs call into the same code, at least for WebGL, the performance behaviour on Chrome between WebGL and Pepper's GL wrapper is basically identical, and most other exposed API features are so similar to their HTML5 counterparts that it is almost certain that there's the same code underneath.
> Sure, but under the hood both the HTML5 APIs and Pepper APIs call into the same code
It's still wasted effort, though. Maybe they share some code, but Pepper is an unnecessary extra API. One that's non-standard and results in vendor lock-in.
The general consensus among non-Google browser vendors was that just using the existing browser APIs was a more desirable approach than Pepper. Since then, Pepper has remained a Chrome-specific technology.