When we created extensions, our goal was (and is!) to enable new types of shared interactive experiences between broadcasters and their communities. We’re bringing extensions to mobile as a step to unify the customer experience across all platforms, so regardless of where you watch, you can participate in extension content.
You bring up a great point about an extension being able to add moderation tools to the mobile experience. It appears, as you describe it, you already have a web version of that extension active (BTTV or FFZ), it’s just not a Twitch Extension! I believe the way we’ll solve for your concern long term is to create more flexible functionality on web such that an improved moderation tool Twitch Extension makes just as much sense on web as it does on mobile and you have access to those tools regardless of platform in a fully supported way.
For now, we won’t be adding the capability for mobile-only extensions.
Thanks for the feedback!