There’s no universal agreed upon definition for a startup but if at all you want to think of one, use growth rate. They have 1000 employees and $1b in the bank now. They had 1000 employees and $500m 48 hours back. They had 500 employees and $250m a year ago. They had 250 employees and $100m 2 years ago and so on..
I have to agree they’re not a startup. By the definition the parent comment provided, a lot of clearly-not-a-startup companies are startups.
How many new hires did Facebook add during the pandemic that are now being fired? Facebook is by no means a startup. It typically works the other way around: gawping headcount by thousands at a time requires the kind of organization that startups typically struggle with.
No “non-startup” can grow at that pace.