Ok, I've looked it up, and a study seems to suggest that:
"Diastolic blood pressure rises, heart rate falls, number of rises in skin conductance, and muscle potential increases, were greater for anger than for fear, whereas skin conductance increases, number of muscle potential increases, and respiration rate increases were greater for fear than for anger."
Butcher, in this scene, is stoic, looking Homelander in the eye, and not flinching. Homelander also has a great deal of experience analyzing people's heart rates, blood pressure, etc, and spends most of his time around people terrified of him. He can see and hear a heart beat, he can tell what's going on with someone at a glance, especially considering he's much faster than Billy, so he's perceiving it way faster.
Sage does not possess the ability to see under someone's skin, and, to my knowledge, is not typically hearing heartbeats from many meters away.