There’s more information on why there are string representations of the IDs in the API overview section. In this case, because you are using Javascript, the language cannot handle the large Snowflake ids being used. You should always use the _str version.
Apologies that you hit this confusion when investigating the streaming API documentation.
Finally, I just want to clarify that you’re using the public streaming API, not site streams (which is a closed beta product).
