Why are the signing employees (at least the anonymous ones) trusting the creators of this website? What if it was set up by someone who wanted to gather a list of all the dissidents who would silently protest or leave the companies or whatever? Do you know whom you are going to hold accountable if it turns out these folks don't delete your verification data, or share it with your employer, or worse?

Also, another warning to anonymous users: it's a little bit naive to trust the "Google Forms" verification option more than the email one, given both employers probably monitor anything you do on your devices, even if it's loading the form. And, in Google's case, they could obviously see what forms you submitted on the servers, too. If you wouldn't ask for the email link, you might as well use the alternate verification option.

Anyway - I'm not claiming it's likely that the website creator is malicious, but surely it's not beyond question? The website authors don't even seem to be providing others with the verification that they are themselves asking for.

P.S. I fully realize realizing these itself might make fewer people sign the form, which may be unfortunate, but it seems worth a mention.

Looks like it supports alternative proof of employment. They don't require disclosing identity as long as they are convinced you work for these companies.

let a thousand flowers bloom

I think it's an important call-out though. Can never be too safe in this landscape.