Yes, as you need to specify the type of Alert. The fact that the list of props is dependent on the selected component type (not a coponent). We have for the component Alert property Message, while the Timer component is not. Therefore, as the component type, choose Alert.
Simply put, by choosing a suitable type, you can extend the functionality of existing components. Do you remember my example to change the font size in the Text Input? It uses a similar decision. I took the components that had this property Font Size and added it to the Text Input component that this property does not exist.
This method allows you to change the properties of some of the components, for which there are no blocks. Not necessarily to create blocks for all components. Enough to create many useful blocks for multiple components, and then apply them to the other. I wrote about this, but if you like this idea, then I ask you to recall Mark about it. Thunkable X can be a very interesting tool, but it depends entirely on the developer and some of us - members.