Unironically, he is a psycho/sociopath.

He doesn’t have genuine emotive expressions.

He only has performative ones.

… This is resting psychopath face.

https://psychcentral.com/health/identifying-psychopathic-stare#non-verbal-cues

Of course the stare alone isn’t enough to ‘diagnose’ him but uh, combine it with the rest of his personality traits and history… doesn’t seem too unreasonable.