Celebrimbor's story in Rings of Power is making Lord of the Rings book readers suspicious

gamesradar.com:

Warning: Major spoilers ahead for The Lord of the Rings: The Rings of Power episode 5! Turn back now if you haven't seen the latest episode on Amazon Prime Video! 

The Rings of Power episode 5 brings nothing but doom and gloom for the Elves. High King Gil-galad shows Elrond that their tree is being corrupted, meaning their own light is fading from them, and both Gil-galad and Celebrimbor are convinced that the only way to save all the Elves from death is the precious metal Mithril – which is being mined by the nearby Dwarves. Last episode, though, Elrond made a promise to his friend Durin that he wouldn't tell anyone about the Mithril, so Elrond refuses to tell the Elves if the metal is in the mines or not. 

But, when Elrond mentions the oath to Celebrimbor, the Elven smith starts telling the story of Elrond's father, Eärendil. He went to the Valar, who are essentially gods, to ask for their help in the struggle against Morgoth. It was a dangerous quest that, in the writings of J.R.R. Tolkien, carried a death sentence. Ultimately, Eärendil was successful and his life was spared, and he now carries the Evening Star through the sky, as Elrond tells Durin in episode 4. 

"I was there, Elrond, the night your father set sail," Celebrimbor tells him. "A mortal man who believed he could convince the very gods to come to war in our aid. I heard your mother pleading with him not to go, asking him, imploring him, why, why must it be him? And do you know what he said? Because he was the only one who could do it." The story has a visible effect on Elrond, and the next time we see him, he's talking to Durin about the Mithril, so it seems this story of his father's heroic exploits has changed his mind. 

But… there's a small problem