This is how you end up with police making up an “anonymous tip” which allows them to gain a warrant and dig through the personal possessions of anyone they don’t like.
The problem isn’t solve with anonymity, but by actually protecting the whistle blowers.
This requirement is designed to be hard, and as such is a major red flag to me.
What else is this company going to be difficult with?
Can i only get customer support or cancel my account in person, between 9-4 on the 2nd Friday of the month?
I would consider alternatives, if possible.