No need to jailbreak to remove pinning; you just need to patch the app itself (for example, by replacing the certificate it verifies against or the code that does the verification).
you need some way to decrypt the app store app so you know what you are modifying and so you can resign which usually involves a jailbreak. maybe there are these apps that only have the first page encrypted so potentially you don't need to decrypt these apps because you can guess what the first page is.