Apple has traditionally locked down mobile Safari to a far greater extent than desktop Safari when it feels there is a compelling UX or security reason. For instance non-fullscreen video is not possible on mobile Safari, but easily doable in desktop Safari and native applications. I'd expect this to be similar at least initially - it could still come to mobile Safari some day, I just think the initial release will be for desktop.

While I understand there's an argument to make on standards for them supporting it in mobile Safari, a mobile web browser is really a lousy place to build software like this. Customers are going to be much happier using a native application. We could certainly get into a discussion on what Google is doing with the mobile web on Android that would make mobile Safari support more important, but Apple is not going to be moving away from installable Swift/Objective-C based applications for the foreseeable future, and that's going to remain the best implementation route for a while.