Cartel is a pretty strong word for what happened and the fact that wages remained high is likely not an anomaly. E.g. Hedge funds which make similarly large amounts of money have paid their employees just as well for many years.

The FAANGs had soft agreements to work together on labor by not hiring each other's workers. That seems to fit the definition of a cartel:

"group of independent market participants who collude with each other in order to improve their profits and dominate the market"

I suppose we might argue that even the FAANGs together aren't large enough to constitute the full market. Other companies compete over the workforce of FAANG-eligible workers. The long tail of such SV employers with lower employee headcount a is still probably large in the aggregate. Though even apart from no-poaching agreements I've seen it speculated that FAANGs may employ large #s of talented people somewhat unnecessarily purely to keep them out of the hands of current competitors or potential startups that could grow into competition. That's a bit too conspiratorial for me though, at least without more evidence

Notably the F did not take part in the collusion.

A recruiter at Google was fired simply for reaching out to an employee at Apple. Cartel feels like an appropriate word.