That was my point - I was correcting your earlier statement "Since Templates are not returned when using the call Get Orgs Network".
Agreed, you cannot update the Template notes, currently. I didn't say you could.
There are a lot of settings that are set by templates that you cannot update via the API in networks bound to a template. This is an area where the API documentation is lacking - those exceptions should be clearly documented, but currently they are not. You only discover it when you try to use an API call and you get an error message stating something to the effect "templated networks are not supported by this endpoint".