If you open a malicous tab, yes. MacRumors or any other reputable site? No. They all have far more effective tools for tracking than this. And, if you’re opening malicious tabs, you likely don’t have to worry about this either as they ALSO have more effective ways of obtaining benefit from your traversal to their malicious site.This isn't limited to iframes, but any tabs that you open during the browsing session. So, any website could be a bad actor and doesn't necessarily have to be an ad network. They could link your Google profile (if logged in) with the tabs that you have open.
What they’re saying is possible, like how walking from Los Angeles to Las Vegas is. Sure, it’s possible, but no one would do it unless they really wanted to do that thing it the absolute worst possible way.