Even banks use derivative verification. (Afgeleide verificatie)
In this case you can open a savings account at another bank, and validate your personal details by paying a small amount of money from a verified payment account from the other bank.

It's about the same way how oAuth works.

The devs have to trust a widely trusted company and use derivative verification. So why not upload a kraken screenshot, and pay a satoshi from a kraken address?

Never give your BSN to a stranger. Even not a part of it.

Some time ago there was a huge fraud on government payments in Amsterdam. Even if the devs are ok, documents can leak. In the Amsterdam case, it was probably caused by leaked/stolen mail.

Personal info like ID cards are worth millions in the underground world. This will work like a honeypot. Sooner or later, they will be hacked.

Be warned, being a victim of identity fraud can give you lifetime problems. Ask yourself if you want to put yourself at risk.