This is VERY common sense. Whenever I heard people talking about how they "wrote their seed in paper and put them in a vault" I laugh. How does that protect you against real life thieves? people in the internet era often forget that real life criminals exist too, and they will try to steal your money. As bitcoin becomes more mainstream, thieves will train themselves to identify how a potential seed looks like. Whenever they see a bunch of incoherent words in a paper they will realize that's an Electrum seed most likely, and then you are fucked, because you either tell them or they may torture you or some other sick stuff.
There are many ways to hide your seeds apart from putting them in a vault. Actually, I think a vault is the worst place.
A thieve wouldn't know I have bitcoin and wouldn't find my seeds because they are hidden among so many papers that even if he was trying on purpose it would take him a long time.
A thieve breaking into my house looks for money and metals and he is not going to be looking through thousands of papers, unfolding them, to try to find money or gold there.