That would be surprising if developers were fungible. You can have a surplus of web developers (whom you lay off) while at the same time have a shortage of AI talent. Those web developers can't be hired in to the openings for AI talent.
I wouldn't call developers fungible, but certainly good developers are adaptable.
If anything, what is the difference between an employee and a contractor if you can just terminate them once you're done with them?
Getting hired (getting an apartment, ...) is easier in the US as there are significantly less challenges at terminating those contracts by the 'provider' than in e.g. Germany, where it's really hard to fire or evict someone.