Google Docs already had an HTML import/export API, which allowed you to download a document, make changes, and save those changes back again. That would allow you to implement any kind of templating you like. This API just makes it slightly easier and more visible.
Yeah that's what APIs do. You can usually work with CURL requests/scraping too, but it always feels clunky and improvised, much like the method you are describing seems to me.
Making something easier means making it more accessible, means the tech based around these tools will advance faster, and that's good for everyone. It's not just a new bauble, well, except it's Google, but it will be very useful until they inevitably abandon it.
Tiny differences in html being sent seem to result in headers working or not, tables rendering differently and more.
> Google Docs already had an HTML import/export API, which allowed you to download a document, make changes, and save those changes back again.
I found that importing an export didn't result in the same looking document.