The typing for Telerik events in Angular that I have seen so far is generally quite mixed in quality. There is heavy use of EventEmitter<any> for some commonly used components, which is a code smell in TypeScript.
It makes it considerably more difficult/risky to develop using these events, as you don't quite know what to expect until you try running it a few times and/or playing around with it on the website sandbox. Furthermore, the sandbox has its own issues too, such as not always making it clear if a value is null/undefined vs an empty string (which does make a difference for how you handle it), so I typically have to make a dummy component and debug it myself just to find out.
See for instance:
Others have a mix of typed and un-typed
A component that does this well by contrast is the Map one, where the events are all strongly typed, making them much easier and safer to use.
In certain cases (e.g. Comboboxes), where a value change emits the selected object/string, or "undefined" (at least as far as I can tell), could it not use generic typing to infer the type based on the type of the provided data, and default to "any" otherwise?
For focus/blur events, at least the switch component provides typing that lets me know it refers to the original DOM event (though it still has "any" on the valueChange - which seems unusual as I'd intuitively expect it to be a boolean).
Even if it is truly impossible to get typing for certain events, there should at least be clearer documentation on the API reference of what you should typically expect to get/where the event comes from.
Component libraries should not require you to guess or figure out what to expect for exported events. Please can you make this a priority in new releases.