That is the rule for all new sellers, as it has been for a very long time

A security/safety measure 

And in part, due to scammers opening accounts to sell things they don't have, or they sell something worth $$$$$ and send a piece of cardboard, take the money, close the account and clear off with the money

You are obviously a new seller and on managed payments.  As an additional security measure new sellers now have funds frozen for 30 days, instead of 21 days under the paypal system