Where are you seeing that? I'm seeing:

>Safari on OS X supports WebDriver, which lets you automate web-content testing. It provides a set of interfaces to manipulate DOM elements and control the browser’s behavior. You can enable Remote Automation in the Develop menu and then launch the server using /usr/bin/safaridriver. For information about library integrations as they become available, see the information about Selenium WebDriver.

Notably, the "on OS X" bit. (Shouldn't that be on macOS? I thought "OS X" was done for!) Equally, you obviously can't launch the server using /usr/bin/safaridriver on iOS.

From article: "Starting with Safari 10 on OS X El Capitan and macOS Sierra, Safari comes bundled with a new driver implementation that’s maintained by the Web Developer Experience team at Apple."

Sorry guys, you're right. It's a bit confusing that Apple doesn't state clearly at all of the new features whether they're iOS / macOS-only.

From the link you shared:

> Safari on _OS X_ supports WebDriver, which lets you automate web-content testing.

I don't see any mention of iOS in relation to WebDriver.