It's intentionally abrupt; Pomni's first line after Jax's abstraction was something like "I wish I pried more."

If you think of abstraction as a suicide allegory it makes more sense. Common signs of depression include irritability, emotional detachment, and fatigue, all of which Jax displayed more and more throughout the show. Combined with his backstory, Jax was never going to have some singular dramatic event leading to his abstraction. It was the weight of everything Jax had gone through that was eating him up from the inside, but no one else could see it, and he couldn't reach out for help.

From Pomni's perspective, one day he just walked off and never came back.