Well, that's quite the plot twist. I wonder what happened. I don't think the demons were being deceptive concerning the purpose name presenting ritual. They were genuinely worried about the Demon Lord going mad. The Demon Lord was also the very first being Reene met from this world, and whenever Reene encountered him in her mind, he was always a reassuring presence, although he did seem desperate to know his own name. So I guess the name presenting ritual was too late? After all, we had seen in chapter 25 that the Demon Lord had been scratching Gaia's tree of life, and had an odd look about him. It appears that there are dire consequences for doing the name presenting ritual late. Names have quite a bit of power in this world, as we've seen when someone attempted to enslave Reene with a blood pact.
I'm really curious about the next chapter. Reene is in a huge bind and definitely needs external help to get out of there. But then what? The Demon Lord is essentially a god...