Why would the seller ask me to do this on paypal?

I was going to buy something from a provate seller, but before I send the money he requested that I uncheck the “security and protection” box so that he can recieve the money instantly and not have the banks hold it for 5 days. He says he wants me to do this because he said he isnt going to start getting the product together and packaging it for shipping until he recives payment. Will I still be protected and able to file a dispute if the sender doesnt send me anything? Or doesnt send me the items as described? Is he being legit and honest or just being sketchy?