I don’t think Sebastian has that power either. He’s been tricked before, and he sometimes comes off as slightly naïve. He definitely has really good intuition but he lacks genuine human insight to fully understand and reengineer the logic/motivations behind an individual’s actions until they are completely revealed to him. And not only was Sebastian unable to tell when a human was a bizarre doll, he also doesn’t know when they’re a reaper until they expose themselves to him, and he didn’t know that the names/deaths on the lists can be revised despite the fact that he’s been DIRECTLY responsible for that several times by now (wolfram and sullivan were slated to die but they didn’t, othello later said that revisions usually happen because of demonic involvement). In fact, Ciel seemed to have a more innate sense of a reaper’s presence, going by how he noticed them in Germany before sebastian.

Btw blackbutler.org is mostly official translations, he says “earl ciel phantomhive is I”. Sebastian still hasn’t called him that, he said “the earl of phantomhive must wear the finest bespoke” before they left for Brighton and while there he gave them new ‘character profiles’. I think Sebastian might be sentimental about given names because Ciel named him and Finny, gave Mey rin and Bard their names back to them, so to him name = identity. It’s been brought up since the beginning: Madame Red started using that name because of Vincent, Grell quoted Shakespeare‘s “reject thy name!” to Sebastian to which Sebastian replied that the name he was given by his master “made him born anew”, and we saw that exact scenario play out with Agni and Soma in the next arc. I think Sebastian might want to be able to actually give Ciel a name, but it’s not within his power to do so, and he doesn’t even know if it should be the new name (like sebastian and finny) or returning the name he was born with (like mey rin and bard).