That's an interesting observation. I'm interested in the answer/discussion.
My hypothesis is that Google doesn't necessarily detect specifically Selenium/WebDriver, but by timing/speed of the account creation. Bare in mind that Selenium and any automated (ro)bot will obviously create (or sign up) an account very fast, much faster than how a normal human does it. So by detecting the speed at which the account was created (from server or client side), Google can guess whether it was a bot or not that created it, and bot created ones = to disable.
One could also test my hypothesis by using an alternate tool to create account: making HTTP requests without going through UI - sorta like screen scraping, and using Google APIs; using AutoIt; using Sikuli; using QTP; using watir; using Appium; using ios-driver; etc. If same result happens then Google didn't detect Selenium but rather something else like timing. If result different, then maybe they do detect Selenium.