I've seen a lot of companies list logos if just a single engineer or team is using the product.
Fair haha. I'm no trademark lawyer, but I have to assume there's some wiggle room when you're not actively stealing their trademark and just referencing it... but still, the combined value of endorsements from Google/Nvidia/Amazon/ByteDance/Tencent/Alibaba/SalesForce/IBM etc has to be worth... a lot. That "not company endorsements" is rather load-bearing. I don't think I've seen anyone just say that, so maybe they're being a bit less bold haha.
You might as well say Herdr runs on 3 billion devices, go all in! 16 billion devices! Every human on earth installed Herdr twice! (source: study amongst users of herdr, n=5)
I go from company to company just to be able to add their logo to stuff I use :)
I used to work at BigTech in a role where I spent a lot of time reviewing new open source projects. It was always a fun game to guess which single person in which department tried out a piece of software that caused our logo to end up on the "as used by..." description on the tiniest of projects.