This article is using “contractor” to mean whatever they want it to mean. They’re not talking about highly paid independent software developers working on contract. They’re talking about at-will employees of a third party that Google contracted with to fill low-skill positions.

That's not "whatever they want it to mean". That's industry standard terminology. And it's not all low-skill positions. A friend of mine is a PhD optics researcher and he was a Google contractor (the employee of a third party kind) for a few years before moving on to an FTE position elsewhere.

The difference is that contractors can be removed from the company without any action on part of the employeer. If an employer wants to remove contractors one option they have is to do nothing and let the contracts expire. They cannot do that to an employee. They must explicitly tell the employee that their employment is being terminated.

Even for higher skilled "contract positions" you don't seem to command a premium in the USA.

The positions in question here are basically lower-tier quasi-employees, who are contracted through an employment agency because Google doesn't want the liability of employing them directly. That liability is both legal and reputational, the latter because cutting contractors lets Google cut costs without worrying their FTEs. These contractors work full time for a single client (Google). They expect/hope to do so indefinitely, at least for a year or so, and in normal times they do.

I believe that UK-style contractors are closer to what I'd probably call a "consultant", specialists who get a much higher hourly rate than an FTE would but aren't sad or surprised when a contract ends. Those do exist in the USA, but that's quite different from the "contractors" here.

I have seen people getting paid a lot on contracts. But of course it depends who considered them high skilled - Company contracting them or contractor themselves.

Got to keep this discussion in context. Google has no need of hotshot contract programmers. That company already has 50000+ crackerjack programmers and they decline to hire 99% of the candidates who want to join them. In the context of this article, the contractors are people who would not be qualified for full-time engineering jobs at that company. They are performing peripheral business functions or grinding on manual tasks like content moderation.

I think contracts come with clauses that enable either party to give notice and terminate the contract. As to whether or not you get 2 or 3 times the FTE that is highly variable. You wouldn't necessarily know what the FTE rate is. Typically you would see an advert with a specified rate, be recommended or brought in by someone already there. Either you would be made an offer. If you like it you go for it.

FTE for the industry is fairly easy to get and contract agencies will know what the rate is.

I know what the day rate for my skills are £700-800 for central London - though that doesn't factor the commute so probably ought to be a bit more.