The right Layout grid for iOS UI design

I just downloaded the free iOS 13 GUI for figma and I tried to see whether their app templates follow a standard grid layout format, and by the way it looks they don't - components are not aligned across the grid in a particular way. So I was wondering if I have to follow a strict layout grid guideline for iOS design or should I just create my own? I know that some people prefer to use a 12-layout or 6-layout grid template but for me it feels kind of weird aligning my design elements around a 12-layout or 6-layout grid template and I would rather use something more customizable to my own design needs. Any clarification would be much appreciated.