Should I submit all 12 words? It's just that nobody ever asked me. My question may be weird but I was expecting another kind of answer
No, don't send. The request is weird indeed, it's good that you noticed. Most likely you found a scammer, a blockchain.info impersonator. BTW, the website is blockchain.com now.
But you opened 2 topics on this same problem, please close this one and continue the discussion in the original topic.