First of all, there is no way to know your information is not being stored. If you are sending your details and data to a third party, you have to completely take them on their word that they will delete it after they are done. You need to trust them completely. There is also the possibility of your information being intercepted in transit or accessed by someone other than the intended recipient.
Second of all, I'm not sure what this achieves. KYC on centralized platforms is so they can comply with government regulations, and on decentralized platforms such as this it is seen as a security measure to help prevent scamming. If I verify my identity, and then all record of the verification is wiped, then what has really changed? A CEX can't prove to the government I am who I say I am because all my information has been deleted, and a trader on a DEX can't hand my details to the police if I scam because all my information has been deleted.