Welcome to the forums @VitaminB.
This is pretty much the landscape and more common these days with a variety of lenders plus there are plenty of recent posts from other members where such additional supporting documentation was requested to process an application (personal and/or business accounts).
You don't have to comply with the request if you are unwilling to do so, but they're also not required to lend/open an account in the absence of such information. Their bank, their rules. Other lenders who are known to require this information from time to time include American Express, Citi, Discover, FNBO, Bank of America, Capital One and a variety of regional banks and Credit Unions.
