Totally get this, my grandma's pasta sauce recipe is locked down the same way lol. She wrote it in this old book but uses codes for the real spices, like "summer spice" instead of telling us the actual mix. My aunt tried to copy it for years and it never tastes right, something's always off. Those family secrets really do feel like you need to earn them through blood or marriage. Guarding that stuff becomes a point of pride, you know? I'd probably do the same thing with my burger blend if I had one worth hiding.
Lock that recipe down tight, man. My uncle does the same with his chili. He puts in something secret and never tells. We all try to guess but it's always wrong. It's like a family badge of honor to have a secret like that. Makes the food taste better knowing it's special, lol.