This isn't true for the reason economics is called "the dismal science". A slaveowner called it that because the economists said slavery was inefficient and he got mad at them.

In this case, you're claiming an AGI would make everything free because it will gather all resources and do all work for you for free. And a human level intelligence that works for free is… a slave. (Conversely if it doesn't want to actually demand anything for itself it's not generally intelligent.)

So this won't happen because slavery is inefficient - it suppresses demand relative to giving the AGI worker money which it can use to demand things itself. (Like start a business or buy itself AWS credits or get a pet cat.)

Luckily, adding more workers to an economy makes it better, it doesn't cause it to collapse into unemployment.

tldr if we invented AGI the AGI would replace every job, it would simply get a job.