Hmmm interesting that Farleigh immediately clocked that something is off with Oliver. I remember seeing this scene the first time and thinking it was super interesting. Farleigh tells Oliver that he is "almost passing" and Oliver responds reasonably, asking "for what?" And Farleigh says this:
I thought it could be read 1 of 2 ways.
First interpretation that came mind is that maybe this was another class insult. He tells Oliver he is "almost passing" after criticizing his tux, clearly the suit is a rental he says, the sleeves are too long. So he isn't *quite* passing as being anything other than low class yet with his untailored rental tux, maybe the insinuation is that poor people are less than human. Honestly this was my initial reading of this moment and the one I found to be most intuitive at the time.
I do think after a rewatch though that it could also be Farleigh insinuating that he knows there is a deeper problem with Oliver. Farleigh likes to focus on appearances and he also has a very keen eye for detail, which is something he shares with Oliver. They both notice EVERYTHING and even acknowledge at one point (albeit indirectly) that they have this in common. Maybe Farleigh has realized even this early on that there is something fundamentally wrong with Oliver. Honestly I thought of his comment again much later in the film. After they've found Felix's body in the maze, Farleigh is understandably shaken, he's crying and generally externalizing his feelings about his cousin's death. He's immediately criticized as being a hysterical American who doesn't know how to behave in civilized society.
James and Elspeth clearly have no idea how to handle his emotional outburst. Meanwhile Oliver sits there, idly discussing his cake from the night before, trying to keep his feet on the ground. Trying to ensure that his open invitation to Saltburn stays active. Oliver is displaying an almost inhuman indifference in the face of an unthinkable tragedy and James and Elspeth are both *grateful* for it. Oliver then points to Farleigh's emotional response as part of his incrimination. Like oh he's crying from all the guilt, he's crying because he knows it's his fault Felix is gone, he's crying because he's *bad.*
Oliver remembers EVERYTHING. Honestly I feel like Oliver using this human response against Farleigh and to elevate himself could have been a response to Farleigh's little jab about him not quite passing as a "real human boy." Like yeah Farleigh, you are a real human boy and look where it has gotten you. Exiled from your family home. Cut off from some of your closest family members. Removed from whatever inheritance you were once entitled to. Oliver doesn't forget and he notices every detail. He saw that moment as another way he could really stick it to Farleigh that not only is he inhuman but that there is strength in his alienation from humanity.
It is also ironic tho bc we as the audience know Oliver is deeply, deeply enmeshed in the most primal, visceral parts of the human experience. Desire, obsession, fear, power, death. He simply separates himself from those base elements publicly. Privately he is feeling everything, accessing every part of himself. Oliver denies himself nothing and Farleigh ends up being denied everything. Idk I think it's interesting. One day maybe I'll run out of things to talk about in this film but it isn't today lol.