Come on. If Google broke ranks and started aggressively poaching people for GCP and going after market share, Amazon would realize in about 5 seconds that it hadn't "overhired" for absurdly-profitable AWS after all.
These firms have colluded to drive down wages before (the "Techtopus" case), a fact that we know because they were stupid enough to put it in writing. This time there's no proof and may be no explicit agreement, but a tiger doesn't change their stripes.
The way most of these companies are colluding now is by using third party firms that "aggregate industry salary information". So basically company X provides their data, pays some dollars, and get access to what other companies in their "peer set" are paying for different types of levels/experience. Reminds me a lot of the schemes companies will sometimes use to do bribes in other countries -- paying a third party consultancy who they had "no possible way of knowing that they were actually just bribing people".
