What part of a "persistence method" are not using vulnerabilities? If you infect the boot loader, bios, firmware, or some other methods to create persistence then those are vulnerabilities. That a system can get infected in such way is not by any intended design.
Could give an example of a persistence techniques that is using a intended feature of a computer system in order to hide the malware in unintended places in such a way that the system can't remove it (which itself is a unintended functionality).
Could give an example of a persistence techniques that is using a intended feature of a computer system in order to hide the malware in unintended places in such a way that the system can't remove it (which itself is a unintended functionality).