Yes, not sure I am following you, but I think MIT app is more capable of doing lots of custom things. And BangleJs needs it’s very own app to interact with. Basic use case of app where you can push latest news, announcement and update. Very own way to send notifications to BangleJs.
Web Ble App Store works grate for installing and updating apps but it is not practical to do everyday “smartwatch” stuff from mobile browser as a use needs a lot user actions to perform a simple task. A dedicated app would make more sense to me.