I shouldn't need to sign anything because my account wasn't hacked. I still know my password. I still have access to my email address. I just need someone to unlock my account.
In 2015, there was a database leak, and many accounts got hacked. Those that didn't, got locked. You will STILL need to provide proof YOU are the actual owner of the account. You WILL need to sign a signature to do that.
You are not the first person who had to do this. If you want the account back, this is THE ONLY WAY to do so.