What you've heard is right. If things keep progressing the way they are now, Kbin will also have mobile apps. It's just that Kbin's Application Programming Interface (API) isn't finished yet. That's what app developers need in order to easily make an app for Kbin. Lemmy does have an API, so that's where most of the app development is taking place right now.

But Kbin will make it's API available and there will be mobile apps for Kbin. I'm aware of at least one app that's already in development, Artemis. The developer has a magazine here with a pinned FAQ: /m/Artemis.