If you're going to build a loading indicator, you may as well go for a skeleton UI rather than a spinner. It's better UX practice because it lowers perceived load times and is much less jarring to swap in and out.
The two are not mutually exclusive. Yep, a skeleton UI is great for filling out the canvas, but the addition of a spinner can indicate that "more stuff is coming".
I agree. A skeleton is good practice because you are progress and a spinner is great because it's allowing the user to understand the webpage is still loading which isn't always obvious.
Google started doing this in Maps and I didn't know what it was or that it was intentional until I saw your post. My impression was that it was just an amateurish mistake of showing the unpopulated template.