Correct, UI for UWP is a suite of components for XAML (C# or VB) applications and you can't render a XAML control in an HTML based application.
If you're looking to use a Telerik product in an HTML based UWP app, you could use an HTML based product, like Kendo UI, by leveraging the UWP Hosted Web App
Lance | Tech Support Engineer, Sr.
Telerik by Progress
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items