I have fake contact forms, non-existent myles, phone numbers that don't actually work and generated credentials on many sites. How far do you think ps goes in validating user experience? Downgrading for forms that accept messages but then the messages don't go anywhere?

No, I don't think google or yandex go that far. So no need to be wary of fake forms or phones for that matter.

Rather it's positive as commercial and you're improving the site for the PS.

About the requisites - huge doubts, but it is difficult to prove their verification by search engines.

You know about the positive impact of adding to Yandex and Google Businesses. It's hard to say for sure about fake credentials.