None of the BigTech firms have unlimited PTO unless you consider NetFlix “BigTech” and by market cap, they aren’t.
I’m not going to look up the PTO for other BigTech companies. But the one I worked for (Amazon) had 15 days PTO and 5 personal days.
And most people who have defined PTO, also don’t take all of their allocated days off.
https://www.pewresearch.org/short-reads/2023/08/10/more-than...
That’s not evidence of defined vs unlimited PTO as a limiting factor of UPTO.
And because of laws in different states, companies with unlimited PTO also often have a separate bucket for sick time.
Do you consider Microsoft "big tech"? It switched to UPTO back in 2023, just in time for layoffs. And I can tell you that it was a very unpopular move among rank and file.