Looks like WhiteNoise is right but they must have just did this as it was there two days ago when I first installed Obsidian. Thanks everyone for responding!
I am on Obsidian 0.14.15 so this may have changed in the Insider version, but for me I can also see the Sandbox vault with the formatting advice (in a separate window from the vault I have open) via a button on the “Show debug info” command from the command palette.
That is too bad. I much prefer the Help Vault rather than opening a web page. I think I understand why, but it was much better to access everything through the Obsidian app.