Yes,
The only requirement, as shown on that page, is that you set your domain's nameservers to ns1.x10hosting.com and ns2.x10hosting.com (Webs.com should allow you to do this). If you don't set the nameservers, the domain will not resolve to your x10 account. That is the "check" that is performed, as if the nameservers are pointed elsewhere, then x10 won't serve the page for that domain. That's why you can't just set facebook.com as your domain, because the nameservers aren't at x10